Neutron activatable tracer-labelled particles were used to study the aerosol deposition for both smooth and ribbed surfaces of a duct under turbulent flow conditions. Spatial distribution of aerosol deposition along the horizontal upward-facing ribbed surface was experimentally determined. For four particle sizes in the range 0.7-7.1 mu m, pronounced aerosol deposition was observed on the Frontal and top surfaces of the ribs, and particle deposition enhancement, on the ribbed surfaces relative to a smooth surface, as high as seven times was observed. The presence of repeated square ribs on the duct surface caused a pressure increment of 3.2. relative to a smooth duel. Efficiency ratios (pressure drop-weighted aerosol deposition enhancement) greater than unity were evaluated for the four particle sizes studied.