The approach to working capital management significantly affects the performance of companies. Nevertheless, this effect varies depending on the observed industry and company’s size and it may be assumed that it is also dependent on territory differences. The paper presents an empirical research aiming to identify particular links between net working capital and costs of the company. The outcomes indicate a relatively strong positive correlation between the variables, especially in case of inventory. Furthermore he ratio of financial costs to ordinary costs is low, as well as the impact of net working capital components on financial costs. It follows that a focus on collection period would not lead to significant savings. The findings appropriately complement Czech and foreign literature focused more on impact of net working capital or working capital on profitability indicators. Further studies concerning a more detailed analysis of the influence of net working capital on corporate costs are difficult to be found. The present research has been conducted on medium-sized companies located in the Czech Republic and manufacturing machinery and equipment. The obtained results suggest the most suitable area of focus for optimization of working capital in relation to costs for the types of companies defined above.