Indoor air quality in restaurants was studied in two cities in northwest Ohio after clean indoor air ordinances had been enacted. Carbon dioxide and ultrafine particles were measured in two restaurants in Toledo and two restaurants in Bowling Green. One restaurant in each city was smoke free, and one restaurant in each city contained a dedicated smoking room. A smoke free office space was also assessed as a reference site. Measurements were collected with datalogging instrumentation simultaneously in both the designated smoking room, if present, and in the nonsmoking section. For smoke free establishments, datalogging instrumentation was also used. Carbon dioxide levels were elevated in all four restaurants, with only 32% of the measurements meeting the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) criterion level of 1000 ppm. Ultrafine particles currently do not have any formal standard or guideline. Statistically significant differences were evident between all four restaurants and the reference site. The largest differences were found between the two designated smoking rooms and the reference site (p < 0.001), with the mean levels in the smoking rooms up to 43 times higher than in the reference site. The results from this study indicate inadequate fresh air supply in all four restaurants, particularly in the designated smoking rooms, and the possibility that the designated smoking rooms were not containing the environment tobacco smoke, based on the ultrafine particle concentrations measured in the nonsmoking areas of the smoking restaurants.