High-resolution (0.001 cm(-1)) coherent anti-Stokes Raman spectroscopy (CARS) has been used to study the v, symmetric CO stretching mode of the quasi-linear molecule carbon suboxide, C3O2. Q-branch transitions are seen that originate from the ground state and from thermally populated levels of the nu(7) CCC bending mode, which is of unusually low frequency. The intensity variation of the Q-branch features on cooling to about 120 K in a jet expansion requires the reversal of the order of assignment given in a previous Raman study at low resolution. The identification of the nu(1) Sigma(g)(+) <- Sigma(g)(+) transition from the ground state is confirmed by the absence of J(odd) Q-branch lines in the resolved CARS spectrum. Analysis of this band in terms of a quasi-linear model gives a good fit to the observed transitions and leads to vibrational-rotational parameters (in cm(-1)) of nu(1) = 2199.9773(12) and (B' - B '') = -2.044(6) x 10(-4). Other transitions originating from higher nu(7) levels occur at only slightly lower wavenumber values and permit the calculation of the double minimum potential in the Q(7) bending coordinate. The results indicate that the ground-state barrier to linearity (21.5 cm(-1)) increases by only 0.6 cm(-1) when the CO symmetric stretch is excited.