The spread of flexible working hours has increased sharply in recent years. Usually the decrease of overtime and subsequent reductions in costs are stated as a motivation for the implementation of flexible working hours. That the implementation of an new working hour scheme will also lead to a change in working conditions, is usually not taken into account. Especially the individual time sovereignty of workers is affected which may have consequences for the expected income. Therefore this project analyses which companies use flexible working hour schemes and how these are related to other factors in the company (e.g. capital intensity, profitability, fluctuation). Furthermore the interrelation between the working hour scheme of a company and the income of workers is analysed in order to draw conclusions on the assessment of the flexible working hour scheme by the workers. Finally the firm-specific efficiency gains from using flexible working hours is investigated. Keywords: working hours flexibility, efficiency, compensating wage differentials.