The paper deals with Czech sickness insurance, which is built on principles of social insurance but utilizes a few additional concepts and covers short-term inability to work. The reasons for this inability however differ and recently new covered situations arose. At the same time, the discussion about the replacement ratios and the parametric setting of sickness insurance's waiting period took place, also in public discourse. The paper, albeit selectively given its length, focuses on those issues and explains their consequences for the participants and the coverage of social situations. Also, it points out the benefits' sense and emphasizes the importance of social sickness insurance approach within public finance and social administration, as well as its principal features and factors that influence its balance and performance.