Photodynamic Therapy (PDT) is a treatment method that combines photosensitizers (PS), specific wavelengths of light, and oxygen to target and kill cancer cells. This review explores the principles and applications of PDT, highlighting its role in modern cancer treatment strategies. PDT has a long history, dating back to the early 20th century, and has evolved to be used in dermatology, oncology, and dentistry. The key components of PDT include the accumulation of PS in cancer cells, the activation of these cells by light, and the production of reactive oxygen species (ROS) that induce cell death. Recent advancements have focused on improving the selectivity and efficacy of PDT, such as the development of activatable multifunctional PS and the use of high-power light-emitting diodes (sLEDs). PDT is particularly effective in treating skin cancers, including actinic keratosis, squamous cell carcinoma, and basal cell carcinoma, as well as other cancers like brain, head and neck, and gastrointestinal cancers. Despite its benefits, PDT faces limitations such as light penetration, oxygen dependency, and side effects like pain and photosensitivity. Further research is needed to optimize PDT protocols and enhance its therapeutic outcomes.Photodynamic Therapy (PDT) is a treatment method that combines photosensitizers (PS), specific wavelengths of light, and oxygen to target and kill cancer cells. This review explores the principles and applications of PDT, highlighting its role in modern cancer treatment strategies. PDT has a long history, dating back to the early 20th century, and has evolved to be used in dermatology, oncology, and dentistry. The key components of PDT include the accumulation of PS in cancer cells, the activation of these cells by light, and the production of reactive oxygen species (ROS) that induce cell death. Recent advancements have focused on improving the selectivity and efficacy of PDT, such as the development of activatable multifunctional PS and the use of high-power light-emitting diodes (sLEDs). PDT is particularly effective in treating skin cancers, including actinic keratosis, squamous cell carcinoma, and basal cell carcinoma, as well as other cancers like brain, head and neck, and gastrointestinal cancers. Despite its benefits, PDT faces limitations such as light penetration, oxygen dependency, and side effects like pain and photosensitivity. Further research is needed to optimize PDT protocols and enhance its therapeutic outcomes.