The purpose of this study was to investigate effectiveness of polyelectrolyte in removal of different hydrocarbons and to obtain information on settling velocity, size and density of the floe. Image analysis technique provided multilevel data concerning interactions between hydrocarbons and polyelectrolyte. Captured images were digitized, enhanced by numerous filtering techniques and examined. Additional, video-monitoring system was used to provide information on settling velocity of the floes. Results indicated that polyelectrolyte Cat-Floc 2953, in comparison to EB-5000, was more efficient in removal of all hydrocarbons, which was supported with turbidity measurements, GS analysis and microscopic analysis.