Photodynamic therapy (PDT) is one of the modern approaches in the treatment of tumors and is still in development. PDT requires three components: a photosensitizer (PS), a light source and molecular oxygen. The success of PDT depends on the properties of PS and currently the most commonly used PSs are tetrapyrrole macrocycles: porphyrins, chlorins and bacteriochlorins. Chlorins and bacteriochlorins have a stronger absorption peak in the red region (~ 650 - 750 nm) than porphyrins (~ 630 nm) and it is this physical property that makes them better photosensitizers because light of this wavelength (~ 650 - 750 nm) penetrates deeper into the tissue. The aim of this master thesis was to test the methods of obtaining chlorin from tetra- and tripyridylporphyrins and various attempts were made to modify the diimide reduction and reduction with tin (II) chloride (SnCl2). Reactions were performed on three different porphyrins: 5,10,15,20-tetrakis(3-pyridyl) porphyrin (1), 5-(4-acetamidophenyl)-10,15,20-tris(3-pyridyl) porphyrin (2) and 5-(4-aminophenyl)-10,15,20- tris(3-pyridyl) porphyrin (3). The obtained results showed that the reduction of porphyrin with SnCl2 is regioselective and in the reaction with porphyrin 2 gives almost exclusively chlorin 9. In diimide reduction a mixture of products is formed (initial porphyrin, chlorin, bacteriochlorin, isobacteriochlorin) which is difficult to separate and in this case it has been shown that oxidation of diimide reduction products to chlorin is the best option. Oxidation of bacteriochlorin 8 produces chlorin 10 with impurities. In future studies, separation methods should be optimized and, in reduction with SnCl2, it should be examined whether more chlorin would be formed when more SnCl2 equivalents are added.