The photochemical reactivity of homoadamantylphthalimide 5 and protoadamantylphthalimides 9 and 10 was investigated in solution, in the β‐cyclodextrin (CD) complex, and in the solid state. The triplet excited states of 5, 9 and 10 were characterized by laser flash photolysis. Sensitized irradiation in solution was found to give rise to polycyclic products through a transiently generated higher excited triplet state, not detectable by LFP. Direct excitation of 5, 9 and 10 gives, in addition to the products arising from the triplet state, cleavage products probably generated through a singlet state. Complexation with β‐cyclodextrin changes the regiochemistry of H‐abstraction. In the solid state, 5 and 9 are both photoreactive though state‐dependent product mixtures are noted. Irradiation of 5 affords only one product whereas irradiation of 9 affords the same product mixture regardless of whether irradiation is performed in the solid state or in CH3CN solution.