The aim of this study was to estimate and compare longitudinal dispersion coefficients in open chanel in different vegetation maintenance conditions. Investigations were conducted at the Warszawice agricultural channel. All the data used in this study were gathered during tracer experiment. The experiment was conducted twice, during fully vegetated conditions and after complete cutting and removal of channel and bank vegetation. A fluorescent substance, rhodamine WT, was used as a tracer. Five cross-sections were selected and the tracer was released at some distance upstream of the first cross-section. Water samples were collected manually in each cross-section at chosen intervals. Rhodamine temporal concentration curves were obtained through analyzing water samples in laboratory with a fluorometer. Longitudinal dispersion coefficients were estimated for four sub-reaches between each two cross-sections, using method of moments. In the first experiment, lower longitudinal dispersion coefficients were obtained for sub-reaches with thicker vegetation coverage. In the second experiment, conducted after complete cutting, longitudinal dispersion coefficients for all sub-reaches increased. Differences in values obtained for given sub-reach in both experiments were greater for sub-reaches with thicker vegetation coverage before cutting.