Abstract
The neglecting of Stark broadening in analysis and synthesis of hot stars spectra in some cases could cause errors in abundance determination. We analysed Co II lines in the spectrum of χ Lupi and found two well-isolated and strong lines (λ λ 2022.354, 2027.040 Å) suitable for the investigation of influence of Stark broadening. Since the results for both lines are qualitatively the same, we will discuss only for one of them. Comparisons of synthetic lines with and without taking of Stark broadening into consideration, in the case of the χ Lupi star and for the Co II lines, show that even when Stark width is negligible in comparison with Doppler width, Stark broadening may influence line wings.