The potential energy profiles, governing the dissociation of CH2CHCHO to CH3CH + CO, CH2CH + CHO, and CH2CHCO + H in the ground state as well as in the excited singlet and triplet states, have been determined using different ab initio quantum mechanical methods with a correlation-consistent atomic natural orbital basis set, cc-pVDZ. The most probable mechanism leading to different products is characterized on the basis of the obtained potential energy profiles and their crossing points. Also, the geometric and electronic structures of some low-lying electronic states of acrolein, methylketene, methylcarbene, and the CH2CHCO radical are determined by the CASSCF computations.