Chestnut flours (CFs) were produced from 3 chestnut samples (Aydin, Kutahya, and Bursa) by 2 different methods (boiled and oven-dried: BOD-CF and freeze-dried: FD-CF). Functional properties and effects of CF addition (10, 20, and 30%) on the qualities of regular and low-fat cookie were investigated. The freeze drying significantly increased water solubility of CFs but decreased their water binding capacity. The emulsion capacity and stability of FD-CFs were higher than those of BOD-CFs. At pH 4, 6, 8, and 10 FD-CFs had better gelation properties. Spread ratio (SR) values of BOD-CF supplemented regular or low-fat cookies decreased with increasing CF levels. Hardness values of CF supplemented regular cookies were generally lower compared to control. SR and hardness values of FD-CF supplemented cookies were higher than those of BOD-CF supplemented ones. Surface colors of the cookies were darker with FD-CF addition as compared to BODCF addition. In low-fat cookies, the sample supplemented with 10% Kutahya FD-CF had the highest taste-flavor value. FDCF supplementation generally resulted in higher appearance and taste-flavor scores than BOD-CF supplementation in cookies.