A　series　of　zinc　phthalocyanines　tetra-alpha-substituted　with　4-(butoxycarbonyl)　phenoxy　groups　(1a)　or　4-carboxylphenoxy　groups　(2a)　or　4-(2-carboxyl-ethyl)phenoxy　groups　(3a),　and　the　corresponding　tetra-beta-substituted　(1-3b)　analogues,　have　been　synthesized　and　characterized.　The　effects　of　the　position　of　substituents　at　the　phthalocyanine　skeleton　on　their　spectroscopic,　photochemical　and　photobiological　properties　have　been　revealed.　When　compared　with　the　tetra-beta-substituted　phthalocyanines,　the　corresponding　tetra-alpha-substituted　analogues　exhibit　a　less　aggregating　trend　in　the　cellular　growth　medium,　a　slightly　higher　singlet　oxygen　quantum　yield　and　higher　photo-stability　in　DMF,　and　a　comparable　cellular　uptake.　As　a　result,　the　tetra-alpha-substituted　zinc　phthalocyanines　exhibit　a　higher　photocytotoxicity　toward　MGC803　human　gastric　carcinoma　cells　than　the　tetra-beta-substituted　counterparts.　Among　all　these　compounds,　phthalocyanine　2a　shows　the　highest　photodynamic　activity,　which　may　mainly　be　due　to　its　non-aggregated　nature　in　cellular　culture　medium　and　high　cellular　uptake.　(C)　2008　Elsevier　B.V.　All　rights　reserved.