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%. Average annual treatment expenditure per capita was US$ 411 for group 1 and US$ 703 for group 2. No association between adherence to GOLD 2013 guidelines and clinical or economic outcomes was identified, possibly due to short duration of study. Adherence to GOLD 2013 guideline was sub-optimal. To promote the adherence to GOLD 2013 guideline, further long-term and well developed studies are clearly needed.