The potential energy surfaces for CH3CONH2 dissociation into CH3 + CONH2, CH3CO + NH2, CH3CN + H2O, and CH3NH2 + CO in the ground and lowest triplet states have been mapped with DFT, MP2, and CASSCF methods with the cc-pVDZ and cc-pVTZ basis sets, while the S, potential energy surfaces for these reactions were determined by the CASSCF/cc-pVDZ optimizations followed by CASSCF/MRSDCI single-point calculations. The reaction pathways leading to different photoproducts are characterized on the basis of the computed potential energy surfaces and surface crossing points. A comparison of the reactivity among HCONH2, CH3CONH2, and CH3CONHCH3 has been made, which provides some new insights into the mechanism of the ultraviolet photodissociation of small amides.