Background: Sickness absenteeism has been a focus of the EU Labour Force Surveys since the early 1970s. In contrast, sickness presenteeism is a newcomer. Based on surveys, this concept emerged in the empirical literature as late as the 1990s. Knowledge of the determinants of sickness presenteeism is still relatively sparse. Methods: The article examines the prevalence of sickness presenteeism in comparison with sickness absenteeism, using survey data covering 725 Finnish union members in 2008. We estimate logit models. The predictor variables capture working-time arrangements and the rules at the workplace. We include control variables such as the sector of the economy and educational attainment. Results: Controlling for worker characteristics, we find that sickness presenteeism is much more sensitive to working-time arrangements than sickness absenteeism is. Permanent full-time work, mismatch between desired and actual working hours, shift or period work and overlong working weeks increase sickness presenteeism. We also find an interesting trade-off between sickness categories: regular overtime decreases sickness absenteeism, but increases sickness presenteeism. Conclusions: Two work-related sickness categories, absenteeism and presenteeism, are counterparts. However, the explanations for their prevalence point to different factors.