The results of shear strength tests of cohesive soils from neighborhood of Stary Sącz (Kotlina Sądecka), similar in terms of grain-size distribution , are presented in the paper. Determination of the influence of moisture content and shearing rate on values of shear strength of tested soils were the main subjects of the test. The aim of paper was also comparison of obtained results of shear strength and results of theoretical calculation of shear strength using simplifying method for evaluation of shear strength of unsaturated soils proposed by Vanapalli et all. [1996]. Results of tests revealed that the increase of moisture content of tested soils causes significant decrease in their shear strength, which has significant influence on cohesion values. Calculations of shear strength revealed that values of soil shear strength determined using simplifying model gave good agreement with results of shear tests, confirming that important role of matric suction on shear strength of unsaturated soils. It was also shown that better shear strength parameters were obtained for soil having lower organic content.