The increasing air pollution of urban areas caused by particulate matter poses a problem for human health. Plants are able to bind the fine dust particles on their surface and to remove them therefore from the air. Therefore, roof plantings can contribute to the reduction of fine particulate matter pollution in cities. To identify roof vegetation forms with high filter ability, suitable test procedures are missing up to now. Trials to identify the filtering potential of different roof top vegetation mats were conducted in a 1 m(3) big Perspex chamber under controlled conditions. Geotextile mats with Sedum and moss vegetation were compared. Uncovered geotextile mats as well as crushed stones were used as controls. In the measuring chamber, artificial particulate matter (fire-fighting powder) was applied and the concentration of particle fractions of 0.3, 0.5 and 1 A mu m over the period of 90 min measured. During 5 min in the middle of the 90 minute measuring period, wind with a speed of 2 m/s in 10 cm height was generated by means of a ventilating fan. Particulate matter binding capacity of different greening mats was determined as difference between the particle concentration after application of the dust (concentration maximum) and the concentration at the end of the trial. After 90-minute dust exposition, significantly lower dust concentrations in the chamber were registered in the treatments with Sedum mats compared to the controls (reductions from: 11.3 % in the fraction of 0.3 A mu m, 30.9 % in the fraction of 0.5 A mu m and 33.4 % in the fraction of 1 A mu m particles). None of the mat variations could bind the particulate matter in the fraction of 0.3 A mu m under wind speed of 2 m/s. However, the moss as well as the Sedum mats reduced the particulate matter concentration of both, 0.5 and 1 A mu m fractions, under wind significantly compared to the controls. The high filter performance of Sedum can be explained due to the high surface of the plants. To what extent plants can bind or uptake particulate matter under outdoor conditions permanently cannot be cleared in this experiment. However, the system allows to measure differences in binding capacity for different rooftop greening sytems.