Presented diploma thesis is focused on evaluation of certain factors influencing beech dimensional lumber warping after drying in Bučina DDD, Ltd. company. It is focusing on observation and evaluation of certain properties and defects of beech dimensional lumber that can cause warp, as well as comparison between the results of warping by two suppliers of dimensional lumber. The dimensional lumber supplied by Tatrak Artimex was of A quality with dimensions 55 × 55 × 400 mm. The dimensional lumber supplied by Kronotimber was of B quality with cross dimensions 55 × 61 mm and various length ranging from 250 to 550 mm. Measurements of cross dimensions, angle of growth rings and initial moisture content were conducted on dimensional lumber from both suppliers. The dimensional lumber was dried in kiln drier using warm air drying. The influence of certain factors concerning warp was evaluated after dimensional lumber was trimmed by a four-cutter machine. The results showed, that under-dimension of dimensional lumber had no effect on warping. Influence of angle of growth rings on cross warping could not be specified, however the results of the measurements point to other factors causing warp of beech dimensional lumber. The influence of red false heartwood on longitudinal warping could be confirmed from the results.