Female technology executives increasingly are banding together to solve what they say is a problem in their own midst: a dearth of women in top positions at emerging tech firms.

Only about 11% of U.S. firms with venture-capital backing in 2009 had current or former female CEOs or female founders, according to data from Dow Jones VentureSource. The prestigious start-up incubator Y Combinatorhas had just 14 female founders among the 208 firms it has funded.

The...