Two-photon excited photodynamic therapy (TPE-PDT) is the use of a chromophore with a high TPE cross section as a photosensitizer in PDT. The quadratic dependence of 2PE on the laser intensity allows high spatial selectivity by focusing the laser beam at a target point and thus preventing damage to healthy adjacent tissue. Additionally, near-infrared light of twice the wavelength of the absorption band can be used to produce the excited state of the sensitizer facilitating biological tissue penetration. Recently we have shown that porphyrin dimer such as 1 has an exceptionally high two photon absorption cross-section of ca 6,000 GM at 780 nm and high singlet oxygen yields. The challenge now is to synthesize biocompatible porphyrin dimers with good cellular uptake while keeping their excellent photophysical properties. We will present the synthesis of new water-soluble dimers, their in vitro one- and two-photon PDT results, intracellular localization, and fluorescence lifetime imaging microscopy.