Anti-Drug Agency) in Telok Bahang were involved. The subjects were interviewed with WHOQOL BREF questionnaires before joining the MMT programme and also after minimum 4 months of joining MMT. Results obtained were used for comparing life style implications among methadone patients before and after joining the MMT programme. Subjects were predominantly of Malay ethnicity (82%). Subjects were mostly aged between 51 to 60 years old (34%). Paired t-test was done on the WHOQOL scores at baseline (before MMT) and after minimum of 4 months enrolment for all four domains. Each domain showed significant improvement in QOL (P < 0.05).The highest improvement was shown in the psychology domain with the mean value increment of 15.13 ± 17.49. Physical domain showed the least improvement with the mean value of 9.39 ± 16.21.This study has proven that MMT have highly contributed to improvement of quality of life among MMT clients in Klinik Kesihatan Bayan Lepas and AADK Telok Bahang.