Mark Zuckerberg may have redefined the image of a CEO with his hoodie and shower sandals, but not all Silicon Valley executives embrace the casual office dress code. In the past, women in tech may have felt in the shadow of a boy's club, but as more take on leadership positions, they are also changing stereotypes.

From Yahoo Inc. CEO Marissa Mayer to Facebook Inc. COO Sheryl Sandberg, here are eight business leaders who are dressing for success.

Related: 10 Lessons from Great Leaders in Tech

Marissa Mayer

Mayer spent 13 years at Google as its first female engineer. She oversaw Google's acquisition of Zagat in 2011, and joined the board of Wal-Mart this year before leaving her position as vice president of location services at Google to become Yahoo's second female CEO.

Her Style: A true engineer, Mayer gave designer Naeem Khan a spec for her wedding gown in 2009, detailing that she wanted scalloped trim, an A-line skirt and lace, preferably with snowflakes.

Related: Marissa Mayer's New Role: Wonder Woman?

 

Alison Pincus

Pincus spent several years in digital marketing and business development at such companies as Walt Disney, NBC and Hachette Filipacchi before merging her passion for online shopping and design to help create the home-decor flash-sale site, One Kings Lane.

Her style: Her go-to work-wear includes J Brand jeans, Vince T-shirts, Isabel Marant sweaters and Céline flat boots.

 

Theresia Gouw Ranzetta

Gouw Ranzetta started her career as a management consultant at Bain & Company and a product manager at Silicon Graphics before becoming the founding vice president of business development and sales at Release Software. In her position at the venture-capital firm Accel, she focuses on Internet and software investments. She's invested in several fashion and beauty companies including BirchBox and ModCloth.

On Fashion and Business: “When it’s a sea of young guys in jeans and hoodies, and the V.C.’s are in their khakis and button-down uniform, it’s kind of a benefit to be different,” Gouw Ranzetta explained in a recent New York Times profile.

Her Style: Her footwear includes Jimmy Choo and Gucci, but she opts for sparkly Converse sneakers for casual weekends. She compares her shoe collection to her male partners’ cigars and cars collections. 

 

Leila Janah

Janah was a founding director of Incentives for Global Health, an initiative to increase research-and-development spending on diseases of the poor, and a management consultant at Katzenbach Partners (now Booz & Co.) before founding Samasource, a startup with offices in San Francisco and Nairobi, Kenya, that connects people living in poverty to small, computer-based tasks that can build skills and generate income. Samasource was awarded the 2012 Secretary’s Innovation Award for the Empowerment of Women and Girls from Secretary of State Hillary Clinton.

On Fashion and Business: “I remember briefly attempting the Adidas and jeans-and-sweatshirt over T-shirt look, but I realized I was trying to dress like a young tech geek, and that just wasn’t me,” Janah told the New York Times. “Fashion is expressing my aesthetic sense just as much as our web site is.”

Her Style: For work she favors tailored Zara blazers, silk scarves she buys in India and chunky jewelry she inherited from her grandmother.  

 

Sukhinder Singh Cassidy

Prior to founding Joyus, a video shopping site based in San Francisco, in 2011, Cassidy spent 18 years as a consumer internet and media executive at companies including Google, Amazon, News Corp. and Polyvore.

Her Style: Cassidy says that she never leaves the house without four-inch heels and at least one vintage item.

 

Ruzwana Bashir

The CEO and founder of Peek.com, a new travel website based in downtown San Francisco, formerly worked at Gilt Groupe and Art.sy, and has a master's in business administration from Harvard Business School.

Her Style: Standard workday attire includes high-end colorful accessories like hot-pink Christian Louboutin heels or a bright orange Hermès bracelet.

 

Sheryl Sandberg

Before joining Facebook, Sandberg worked at the World Bank and as chief of staff at the Treasury Department during the Clinton administration, then as Google's chief of online sales. She's been Facebook's COO since 2008, and has made headlines as the company's first female board number, as well as its most highly-paid employee (reportedly earning $30.87 million in 2011).

Her Style: Her oldest friends like to point out that she was seen sporting leg warmers and blue eyes shadow when she founded Harvard University's aerobics program in the late 1980s. But her style has evolved and she now favors sleeveless sheath dresses by designers like Calvin Klein and knee-high boots or ankle boots by such design brands as Prada.

Related: The Business Model for Disruption

image credit: GeekSugar

Juliet de Baubigny, partner, Kleiner Perkins Caufield and Byers

Before joining venture-capital firm Kleiner Perkins Caufield & Byers in 2001, de Baubigny was a managing director of Ramsey Beirne Associates, a firm that provided executive searches to high-growth companies. Prior to that she was a partner at executive-search firm Heidrick & Struggles, where she led chief executive officer and other high-level searches.

Her Style: Her favorite shopping sites include Net-A-Porter and Kirna Zabete. She says she also uses the web for ideas on how to style clothes. She's consistently named as one of the best-dressed women in Silicon Valley, but she hates to shop. Her solution? Make a wishlist at key times in the year such as fall and spring, and shop online.

Beth Spotswood