The aim of the present study is drawing attention to a problem of employees who are employed on a part-time basis but work extra hours above the hours set out in their employment contracts but still below the statutory working time norm (further herein "contractual extra time" or "contractual extra hours"). The author analyzes three problematic issues in the present legal state: the part-time employees' duty to work extra hours, setting a contractual maximum of additional pay for part-time employees working extra hours, and sanctions relating to the failure of the parties to an employment agreement to specify the extra hours paid like for statutory overtime.