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Mass concentrations of particulate matter (PM10, PM2.5, PM1), lung deposited surface area and particle number concentrations were measured for the first time in all Viennese subway lines inside cabins and in two subway stations, one aboveground and the other underground. The observed data were examined for significant differences between the exposure to fine particulate matter and ultrafine particles. Analysis of the trip averages in the five lines U1, U2, U3, U4 and U6 showed significant differences for PM10, PM2.5 and PM1 (all three mass concentrations: p < 0.001). Medians for PM10, PM2.5 and PM1 were highest in the U1 (73.6, 38.9, 27.1 µg/m3, respectively) and U3 (113.3, 47.1, 26.7 µg/m3, respectively) and significantly higher in the underground subway station than in the subway station on ground level. Regarding ultrafine particles no significant differences were found between the subway lines and no significant differences between the underground subway station and the subway station on ground level; however, new air-conditioned cabins had lower particle number concentrations and both particle number concentrations and lung deposited surface area were higher in cabins with open windows.