A correlation frequently used in practice for the design of the relief cross-section next to the Homogeneous Equilibrium Model is the so-called omega-method. For the determination of the omega-parameter a definition was originally reported by J.C. Leung in 1986. A new expression was proposed by the same author in 1995. Predictions of the critical mass flow rate using both the new and the old omega-parameter formulations as well as the Homogeneous Equilibrium Model are compared for some typical substances. Results demonstrate that the deviations as a rule are acceptable for practical use, if the proposed range of application and recommended property data calculation are respected.