Hydrophobic 5-ALA derivatives were also investigated for use in PDT of skin cancers. These prodrugs are expected to have better diffusing properties because of enhanced lipophilicity and are converted into the parent 5-ALA after breakdown by esterases of the skin. Similarly to other drug molecules, such as anticancer and antiviral steroids and diagnostic agents with different solubility, more lipophilic 5-ALA ester derivatives originate optimal liposomal formulations