Exhibit 21.1 SUBSIDIARIES OF THE REGISTRANT The subsidiaries of the registrant are as follows: Incorporated Percentage of Voting Name Under Laws of Securities Owned ---- ------------- -------------------- The Old Second National Bank of Aurora The United States 100% 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% Maple Park Bancshares, Inc. State of Illinois 100% Maple Park Mortgage State of Illinois 100% Page 58