Stoichiometric and very rich flames of methane have been investigated using nonintrusive laser diagnostics. Absolute concentration profiles of HCO were measured by intracavity laser absorption spectroscopy, and temperature profiles were obtained with laser-induced fluorescence of OH. Premixed CH4 + O-2 + N-2 flames were stabilized at a pressure of 30 +/- 0.3 Torr. These new experimental data were compared with predictions of two models: GRI-mech. 3.0 and Aramco mech. 1.3. GRI-mech. performs better in a stoichiometric flame, whereas Aramco mech. is in better agreement with experiments in the rich flames. Detailed analysis of the behavior of these two models revealed that similar performance is essentially fortuitous and explained by balancing of different reactions involved in HCO formation and consumption.