Photodynamic therapy is an alternative method to surgical methods used in the treatment of cancer and one of its three basic components is photosensitizer. The high singlet oxygen generating capacity, high solubility in common organic solvents, low aggregation tendency and lightfastness are the characteristics that photosensitizers must have. Phthalocyanines with bulky substituents are candidate molecules that can be used as sensitizers in photodynamic therapy due to prevent aggregation in the solutions and improve solubility. Based on these facts in this study, singlet oxygen quantum yield and photodegradation quantum efficiency were calculated to evaluate the potential of bis(4-fluorophenyl)-methoxy-substituted zinc phthalocyanine, which does not form aggregation and has high solubility in organic solvents commonly used in photodynamic therapy applications. The metallo phthalocyanine generated higher singlet oxygen than unsubstitue zinc phthalocyanine. According to the singlet oxygen quantum yield, the addition of bis(4-fluorophenyl)-methoxy groups to the phthalocyanine ring increases the singlet oxygen production. The results show that this phthalocyanine may be suitable candidates as photosensitizers in photodynamic therapy with the singlet oxygen quantum yield values are 0.76 and 0.70 in DMSO and DMF, respectively.