The effect of different in-plane boundary conditions on the critical load and post-buckling behaviour of a uniaxially compressed, simply supported corrugated paperboard panel is examined, with the aim of reducing the discrepancy between model and published experimental results. In-plane boundary conditions with uniform load distribution or uniform compression on the loaded edges, free or constant normal in-plane edge movement and shear free edges, are modelled. Analytical single-term Galerkin and finite element approaches are used. The critical loads obtained analytically and numerically, for different boundary conditions agree well with an analytical reference result.