Photodynamic therapy (PDT) is a novel non-invasive form of light therapy. PDT can be widely applied in various fields of clinical approach, particularly in the treatment of dysplastic conditions and malignant tumours of the brain, gastrointestinal tract, respiratory and reproductive systems. PDT is most frequently utilised in oncological dermatology; however, it could be easily used in the treatment of acne, skin mycosis or viral infections, e.g. HSV infection. The mechanism of PDT is based on the irritation of a chemical, a so-called photosensitizer that was selectively accumulated in a particular pathological tissue, by the light. The outcome of this irritation is a photochemical reaction that transform the photosensitizer into an active toxic substance that destroys the non-functional cells. The advantages of PDT include high efficacy and selectivity, the possibility of multiple administration of light doses and no evident contraindications of simultaneous usage of PDT and other therapeutic methods in patients of various clinical conditions. Moreover, virtually none side effects and excellent cosmetic effects are making PDT a very well tolerated therapy for many patients. Further steps are taken to introduce PDT in the treatments of cardiovascular disorders, e.g. atherosclerosis, eye disorders or photojuvenation of the skin.