This paper presents the research results of skidder Ecotrac 120V productivity in thinning and final felling half-length wood skidding. Terrain research was conducted using time and motion study at two worksites. Worksite A is a mixed stand of beech (48.74%), sessile oak (4.47%), hornbeam (21.06%) and linden (15.65%), aged 57 years, in which thinning was done. Harvesting density was 34.07 m$^3$/ha, and mean cutting tree was 0.63 m$^3$. At the worksite B, in the beech (92.03%) stand, aged 111 years, final felling was conducted. Harvesting density was 89.50 m$^3$/ha, and mean cutting tree was 3.51 m$^3$. Based on the data collected, the structure of the total time consumption and average daily output was calculated (Table 1). The analysis of recorded delays provided allowance time (Table 2). Differences between load volumes, travel speeds, line pulling and winching speeds and time consumption of individual felling site and landing work elements were investigated by a t-test (Table 3 and Table 4). For those work elements that showed significant differences between worksites, individual mean values were used for further calculations, while for the others, new common mean values were calculated. Travel time consumption was calculated based on the average speed and pertaining skidding distance. A significant difference (t = -3.571562; p = 0.000519) was found between load volumes of thinning (3.050 m$^3$) and final felling site (3.717 m$^3$). Differences in time consumption (Table 4 and Table 5) are the most obvious in the group of felling site work elements, and they are a consequence of different line pulling/winching distances needed for forming the achieved load volumes. The projected daily output (Fig. 2) of final felling skidding is in average 21% higher than in the thinning skidding with an average 26% lower costs per unit (Fig. 3). Detail analysis of each work element time consumption showed that harvesting density and mean cutting tree volume have an important impact on difference in productivity and costs. Different harvesting densities affect the felling site work time consumption, thus also affecting the achievable productivity. Besides the above mentioned harvesting density, mean cutting tree volume has an even greater influence on skidding productivity because it enables the formation of preferred load volume at short winching distances by choking fewer half-stems, often with the use of just one winch drum. Therefore, it can be concluded that the possibility of achieving greatest outputs, in given stand and harvesting conditions, lies in the optimal relation between the load size and the felling site work time consumption needed for its forming.
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