The legal regulations and cultural environment for smoking bans in hotels and motels in South Korea differ depending on the type of accommodation. The aim of this study was to assess the thirdhand smoke exposure for hotel and motel guests staying at accommodations who are expected to be relatively vulnerable to thirdhand smoke. Biomarkers for 28 participants were assessed before and after lodging at a hotel or motel for approximately 14 h. Hotel participants had statistically decreased urinary cotinine concentrations after their stay, whereas motel participants experienced increased concentrations. The concentration of nicotine-derived nitrosamine ketone in dust in hotels was lower than that in motels, and the higher dust nicotine-derived nitrosamine ketone concentration in motels had more effect on an increase in urinary cotinine concentration. Both hotels and motels legally allowed smoking in guest rooms. However, the study participants in hotels were less exposed to thirdhand smoke than those in motels.