Photodynamic therapy (PDT) combines photosensitizer, visible light and oxygen, which has the characteristics of high selectivity, minimal invasiveness, low side effect, and allowing repetitive application. The photophysics and mechanisms leading to cell death mediated by PDT have been studied extensively, and PDT has been approved as the modality for superficial tumors and non-cancerous diseases worldwide. For non-dermatogoical applications, the photosensitizers are delivered systemically. Selective therapeutic effect against tumor tissues can be provided by the nature of drugs and tumor physiology. Improved targeting photosensitizer helps preventing damage to the surrounding healthy tissue and lowering dose of drugs and light. The use of nanotechnology in photosensitizer delivery is an attractive approach because nanomaterials may satisfy the need for enhancing PDT efficacy. Recent advances in the use of nanotechnology for PDT application include formulation of biodegradable and non-degradable nanoparticles as passive carriers for photosensitizing agents as well as synthesizing photosensitizer-specific target moiety conjugates for active targeting. This article focuses on passive and active targeting strategies involving nanotechnology to enhance PDT efficacy for cancers.