Exhibit 21.1 SUBSIDIARIES OF THE REGISTRANT The subsidiaries of the registrant are as follows: Percentage of Voting Incorporated Securities Owned by Name Under Laws of Immediate Parent ---- ------------- -------------------- The Old Second National Bank The United States 100% of Aurora The Old Second Community Bank of North Aurora State of Illinois 100% The Old Second Community Bank of Aurora State of Illinois 100% Yorkville National Bank The United States 100% Burlington Bank State of Illinois 100% Kane County Bank and Trust Company State of Illinois 100% Bank of Sugar Grove State of Illinois 100% Page 56