Labour law has been developed in order to protect implicitly ‘typical’ employment relationships, based on a contract of full-time employment for an indefinite period of time. The development of non-full-time form of employment required new legal regulations to secure that workers employed part-time should not be in a  less favourable position in comparison to those being in full-time employment. Polish part-time work–oriented regulations have been evidently created under the influence of the Directive 97/81/EC. The paper focuses on the comparative analysis of the notion of part-time worker in the Directive and the Polish Labour Code and the protection for part-time workers against unequal treatment. In many cases the regulations under discussion implement the Directive’s requirements or they are even more restrictive than the Directive itself however other still has not fully implemented its provisions. For further development of part-time employment it is essential that the requirements of the Directive 97/81/EC should be met.