Legislation banning smoking in all indoor public places was introduced in Turkey in July 2009. The aim of this study was to evaluate the role of smoke-free legislation on the number of emergency department admissions for smoking-related diseases in Kocaeli city. A retrospective analysis was made of hospital records from the first 6 months of 2009 and 2010 (before and after legislation). Total admissions for smoking-related diseases were 83 089 in 2009 and 64 314 in 2010, a 22.6% decrease. Time-series analysis showed that the decreases were significant for bronchitis and lower respiratory tract infections. Emergency admissions for chronic obstructive pulmonary disease, myocardial infarction and allergic rhinitis were lower but not significantly so. The number of patients admitted with asthma showed a non-significant increase. Smoke-free legislation might have important short-term effects on emergency department admissions, but further studies are needed in order to evaluate the long-term effects of legislation on smoking-related diseases.