A detailed singlet potential energy surface (PES) of the CHOP system is investigated by means of MP2 and QCISD(T) methods. It is shown that the chainlike isomer HPCO is the most stable species followed by the chainlike HOCP and trans-HCPO, which are also considered as kinetically stable species, and may be experimentally observable. Furthermore, possible molecular dissociation channels are predicated and the result show that the direct dissociation of chainlike HPCO can efficiently proceed prior to almost all isomerizations, but the isomerizations of HOCP and trans-HCPO towards the lowest-lying HPCO are favorable in energy than their direct dissociations. (C) 2002 Elsevier Science B.V. All rights reserved.