An adjustable band shape calculation model based on the strong collision approximation with inter-branch coupling has been applied to predict line mixing in the 2000)0110, 1220)0110 and in the 1110)0000 Q-branches of carbon dioxide. In this approach, the band shape is calculated using an adjustable parameter to account for line mixing effects, in addition to the usual set of spectral parameters used to describe the band shape. The good quality of the model is proven by comparisons with experimental spectra recorded at room temperature over a widepressure range (1–21 atm). All spectra were recorded using a Fourier transform spectrometer and 25 cm long temperature controlled cell. Thevalues obtained for the adjustable parameter for the three Q-branches are discussed.q 2005 Elsevier B.V. All rights reserved.