This study aims to examine prescribing patterns of COPD medications, adherence to The Global Initiative for Chronic Obstructive Lung Disease ( GOLD) 2013 guideline, and impact of the adherence on clinical and economic outcomes. A retrospective study was conducted at Ramathibodi hospital. All COPD patients receiving treatment during July 1-December 31, 2012 were identified from electronic database. Index date was determined as the first date with FEV1 during the recruitment period. Data on treatment, cost, and clinical outcomes were reviewed for 1 year after index date. The results were included 109 patients. 84 patients ( 77. 06%) and 25 patients ( 22. 94%) were classified into group 1 ( FEV1 ≥ 50%) and group 2 ( FEV1 < 50%), respectively. It was found that group 1 reported significantly lower exacerbation rate ( 26. 19% vs 80. 00%) than group 2. SABA/ SAMA was the most prescribed drugs (97.61% in group 1 and 100% in group 2). Overtreated with ICS was common (63.09%) with FEV1 ≥ 50%.