In the paper there are presented results of laboratory tests of the sedimentation process in a lamella clarifier model, in which also the suspension has been thickened and clarified. The material for tests was the fine particle suspension from a converter plant, for which the achievement of high clarifying effectiveness and high thickening grade is very difficult. As a tests result the hypothesis has been proved, that the simultaneous use of the counter-current and concurrent sedimentation for the suspension clarifying and thickening leads to expected effects.