The purpose of the present work was to study experimentally the indoor air quality status regarding PM10, PM2.5, TVOCs, CO2, NOx, SO2 and O3 in selected differently used areas. A flat on the third floor of a multi-storey building, located at a suburban area north-east of the centre of Athens and close to a heavily trafficked road and two offices of the Environmental Physics Department building at the University campus, in a suburban area were selected for the purpose of the measurements. The experimental campaigns covered several days in each area in order to include different indoor conditions and outdoor concentration levels. Total VOCs and CO2 were measured on a continuous basis at selected locations only in the indoor environment with two sets of portable samplers. Indoor and outdoor NOx, SO2 and O3 were measured with analysers. PM10 and PM2.5 24 hour averaged measurements were taken with the aid of two sets of indoor particle samplers. Experimental results obtained from Offices 1 and 2 indicate that the indoor air quality in both offices is satisfactory with respect to NOx, SO2 and O3. PM10 concentrations are well above the specified limits on days of smoking or closure of windows in both offices. The indoor air quality in Office 1 seems satisfactory with respect to CO2 and total VOCs concentrations measured, even on days when smoking was taking place and windows were kept closed while all occupants were present. In Office 2, both CO2 and total VOCs concentrations are elevated, even on days when the windows were open or smoking was not taking place, but do not exceed the specified limits, indicating poor air renewal. Experimental data obtained from the residence indicate firstly that NOx, SO2 and O3 concentrations in the indoor environment depend directly on the outdoor levels as they presented the same diurnal variation, while the indoor values were lower than the outdoor ones. Surprisingly enough, the total VOCs concentrations in the living room presented high values when windows were kept open indicating strong presence of outdoor sources. Furthermore, activities such as cooking, cleaning, smoking and use of indoor air fresheners further increased the total VOCs levels. Regarding CO2 concentrations, they were almost constant indicating acceptable but not satisfactory renewal of the indoor air. Finally, PM10 concentration measurements were most of the time below the specified limits, with some exceptions mainly related to window opening and cooking.