The separation of the desirable parts of a medicinal plant in air flow is a widely applied procedure. Therefore there has been established the goal to measure flow characteristics of sage (Salvia officinalis L.) and peppermint (Mentha piperita L.) leaves. Leaves were picked from stem and classified according to dimensions in four (sage) and three (peppermint) fractions. The description of fraction collectives according to dimensions, after either manual or laboratory screen sorting, and data entering into log-normal distribution paper, is given by median and standard deviation. The flow characteristics defined by the air velocity of fluidization of a material layer show the possibility of separating sage leaves and stems, due to a significant difference in velocity values, 1.75 m s"1 maximum for leaves and 3.35 m s"1 for stems. Due the difference in flow characteristics the separation of different peppermint leaves fractions is also possible. The values of air velocity of fluidization for large peppermint leaves and stems were not significantly different, 3.50 m s*1 and 4.18 m s" , respectively. Therefore, for their separation, a machine with more homogenous air velocity field is required.