EXHIBIT 21.1 SUBSIDIARIES OF SOUTHWEST BANCORPORATION OF TEXAS, INC. 1. Southwest Holding Delaware, Inc. Delaware 2. Southwest Bank of Texas National Association* United States 3. Mitchell Mortgage Company L.L.C.** Texas 4. SWBT Insurance Agency, Inc.** Texas 5. SWBT Securities, Inc.** Texas 6. Southwest/Catalyst Capital, Ltd. (99% ownership)** Texas * Subsidiary of Southwest Holding Delaware, Inc. ** Subsidiary of Southwest Bank of Texas National Association