Photodynamic therapy (PDT) is a medical treatment that uses photosensitizers (PS), specific light wavelengths, and oxygen to target cancer cells. This review discusses the principles, history, and current applications of PDT in medical practice. PDT has been used for over a century, with early observations dating back to 1900. It has since become a widely accepted treatment for various cancers, including skin, lung, esophageal, and bladder cancers. PDT is also used in dermatology for conditions such as actinic keratosis, basal cell carcinoma, and squamous cell carcinoma in situ. Recent advancements have improved the efficiency and selectivity of PDT, making it a promising treatment option for cancer patients. PDT is also being explored for the treatment of non-cancerous conditions, such as acne, warts, and genital warts. The use of PDT in oncology of internal organs, including brain, head and neck, lung, and gastrointestinal cancers, is also being studied. Despite its potential, PDT has limitations, including the need for precise light delivery and the risk of side effects. However, ongoing research aims to improve the effectiveness and safety of PDT, making it a valuable tool in modern cancer treatment.Photodynamic therapy (PDT) is a medical treatment that uses photosensitizers (PS), specific light wavelengths, and oxygen to target cancer cells. This review discusses the principles, history, and current applications of PDT in medical practice. PDT has been used for over a century, with early observations dating back to 1900. It has since become a widely accepted treatment for various cancers, including skin, lung, esophageal, and bladder cancers. PDT is also used in dermatology for conditions such as actinic keratosis, basal cell carcinoma, and squamous cell carcinoma in situ. Recent advancements have improved the efficiency and selectivity of PDT, making it a promising treatment option for cancer patients. PDT is also being explored for the treatment of non-cancerous conditions, such as acne, warts, and genital warts. The use of PDT in oncology of internal organs, including brain, head and neck, lung, and gastrointestinal cancers, is also being studied. Despite its potential, PDT has limitations, including the need for precise light delivery and the risk of side effects. However, ongoing research aims to improve the effectiveness and safety of PDT, making it a valuable tool in modern cancer treatment.