In this paper the author deals with the problem of compulsory portion, which is the most significant restraint of the freedom of testation. In the Polish succession law the testator may freely decide, who shall inherit his (or her) estate. However the closest members of the family of deceased (such as his children, wife, sometimes further descendants and testator's parents) have monetary claims against the heir. In this aspect, the Polish law is similar to the German or Austrian succession law. It may be noted, that significant financial liabilities towards the family of the deceased may lead to the serious economic problems of the heir. The possibility and the scope of reducing the compulsory portion by the testator and by the courts are analyzed in the paper. The author considers whether the present law solutions are appropriate and what could make these solutions modern and flexible. The analysis deals mostly with Polish law, but additional comparative observations are presented to help in answering the question about the need for law reform. The author deals inter alia with the problem of partial disinheritance, which may lead to the reduction of the amount of the claim of deceased's family member. The position of surviving life partner of the testator is also discussed. Moreover, the article concerns legal provisions, which could be applied by a court in order to adjust liability of legal heir to his personal situation.