The six-dimensional potential energy surface (PES) of the most stable isomer of C2N2 is investigated using the coupled cluster single and double approach with perturbative treatment of triple excitations (CCSD(T)). The full quartic force fields of this molecule and some of its isotopomers are calculated in dimensionless normal coordinates. This quartic force field has been optimized in order to reproduce the known overtones within 1 cm(-1). A set of spectroscopic constants is derived for these isotopomers using this optimized quartic force field. The full rovibrational spectrum is also given up to 1500 cm(-1) with an accuracy better than 1 cm(-1). (C) 2001 Academic Press.