It is important to analyze and predict ETS particle behavior in rooms for the evaluation of smoking environments and the development of control technologies. As control technologies for ETS, we have developed ventilation and smoke separating systems, in trains, airplanes and offices. Recently, we are trying to find solutions for tobacco odour and the stains from ETS particle deposits. The deposits on walls and furniture appear to be a part of environmental concerns. We studied ETS particle deposition phenomena with both experiment and numerical simulation. The sidestream smoke and the exhaled smoke from a smoking machine were generated in an experimental chamber room. The particle concentration and the size distribution were measured by the particle counters. The experimental results were compared to calculated ones using coagulation and deposition models of aerosols, and they were in good agreement. The deposition rate of ETS particles increases with the turbulent intensity in the room. We can predict the amount of deposited ETS particles, with the air exchange rate, according to the type of tobacco products, such as normal tobacco and low emission types.