Photodynamic therapy (PDT) is an attractive, non-invasive therapeutic procedure successfully used in oncodermatology for the treatment of numerous skin cancers. Photosensitizers commonly used in PDT by dermatologists are the prodrug 5-aminolaevulinic acid (ALA) or its methylated ester (MAL), which are converted to protoporphyrin IX (PpIX) inside the target cells. The activation of photosensitizer by an artificial light source (conventional PDT) or by sunlight (daylight PDT) leads to the production of reactive oxygen species (ROS), with destruction of target cells and induction of immune modulating response. In oncodermatology, PDT has well-established indications, such as actinic keratosis, Bowen’s disease (SCC in situ), and superficial and thin nodular basal cell carcinomas. Recently, treatment of cancerization field and cutaneous T-cell lymphoma with PDT has shown encouraging results. In this chapter, we will provide an overview of the mechanisms of action of PDT and its anti-cancer properties. Then we will analyze both approved and emerging indications of PDT in oncodermatology, with a look on differences between conventional PDT and daylight PDT and the advantages of combination therapies.