Flatworms (Platyhelminthes) are phylum of animals that have extraordinary ability of regeneration, which they keep during the whole life. Among them, planarians (Turbellaria) have the most powerful and the most explored regeneration. They can regenerate all the tissues including the ganglia and this is very rare in nature. On the other hand, flukes (Trematoda) and tapeworms (Cestoda) do not have such powerful ability of regeneration, but as they are parasites, they often cause human diseases or diseases of domestic animals. Because of that, scientists are studying their regeneration for the purpose of finding new, more efficient medicines. In this essay the basic topics about flatworm regeneration, especially in planarians, have been presented. Planarians have become the model organism for studying regeneration because they are easily bred in a laboratory, they have simple life cycle and there are some advanced methods for gene expression manipulation, visualization od specific cells and tissues and tracking of morphological and cellular dynamics. There was a big improvement in characterization of neoblasts – the cellular agents of regeneration, finding mechanisms of polarity in different body axes, determining the role of differentiated tissues and the role of reactive oxygen species in planarian regeneration. A lot of genes that are expressed in the regeneration process have been discovered. However, their regulation has not still been studied enough. Beside regulation, there are plenty of unanswered questions about regeneration of flatworms, and so there are still numerous opportunities for future research in this field.