In order to detect the mutation patterns related to Lamivudine (LAM), Adefovir (ADV) and Entecavir (ETV) resistance, we examined totally 230 stored HBsAg (+) and HBV DNA (+) sera samples of patients suffering chronic hepatitis B and treated with LAM, ADV and ETV in the south of Turkey. 100, 110 and 20 sera were obtained from patients treated with LAM (for at least 2 years), ADV (for at least 2 years) and ETV (for at least 1 year), respectively. A 422 bp segment of HBV polymerase gene which included B, C and D domains of viral polymerase gene was amplified by a nested PCR protocol and sequenced by a silver staining based cycle-sequencing reaction. Mutation patterns related to LAM, ADV and ETV resistance were detected in 23 of 100 (23.00%), 3 of 110 (2.75 %) and 0 of 20 (0.00%) sera in 3 groups, respectively. rtM204I and rtM204V-rtL180M dual mutations were detected in 13 of 100 (13.00%) and 10 of 100 (10.00%) sera, respectively in LAM treated group. rtN236T mutation was detected in 3 of 110 (2.75%) sera in ADV treated group. rtM204I and rtM204V-rtL180M mutations were also detected in 8 of 110 (7.27%) and 5 of 110 (4.54%) sera in ADV treated group. No mutation pattern was detected related to ETV resistance. However, rtM204I mutation was also detected in 3 of 20 (15.00%) in ETV treated group. Additionally, some undefined mutations such as rtI233V, rtN238R, P237H and rtK241E were detected in 3 of 110 (2.75%), 2 of 110 (1.80%), 1 of 110 (0.90%) and 1 of 110 (0.90%) sera, respectively in ADV treated group. The study reveals that detection of mutations associated with viral polymerase inhibitors is important for better patient treatment. Antiviral therapy of hepatitis with viral polymerase inhibitors is still controversial.