Packed beds of spherical particles in a cylindrical vessel have a high porosity region next to the vessel wall that allows preferential fluid flow. Consequently, there are radial variations in porosity (e) and superficial fluid velocity (U) that depend on the vessel-to-particle diameter ratio (D/dp) and the flow regime of the fluid. This work ascertained if these radial variations affected SuperCritical (SC) CO2 extraction curves of oil from pre-pressed seeds at 40 °C and 28 MPa, as compared with the commonly adopted plug flow condition. It focused specifically on comparing extraction curves as a function of the controlling mass transfer mechanism (characterized by the dimensionless Biot number, Bi) and D/dp ratio. A predictive model was adopted to describe the SC-CO2 extraction of oil from sheared seeds comparing plug flow with radial variations in superficial CO2 velocity, U(r), from literature correlations. Selected independent variables included the initial oil content of the substrate (132.7 ≤ Co ≤ 397.2 g/kg), dp (1 or 2 mm), U (1–4 mm/s), and vessel volume (0.038–495 L). Co markedly affected the effective diffusivity of the oil (0.780 ≤ De ≤ 6.24 × 10−10 m2/s), whereas dp and U moderately affected the film mass transfer coefficient (2.44 ≤ kf ≤ 7.40 × 10−5 m/s). Radial variations in superficial CO2 velocity decreased extraction rates, with differences between extraction curves when considering plug flow or adopting U(r) diminishing as Bi increased for D/dp = 20, or as D/dp increased for Bi = 18. Bi increased by increasing U and kf, or decreasing Co and De, whereas D/dp increased by increasing vessel volume. The radial variations in porosity in a packed bed and associated changes in superficial CO2 velocity may have a more pronounced negative impact in laboratory or pilot plant extraction vessels (small D) than industrial vessels (large D), mainly when extracting small particles and applying large superficial CO2 velocities. A proxy for the SC-CO2 extraction of oil from pre-pressed seeds in an industrial extraction vessel (495-L capacity, D/dp = 270) would be plug flow using the porosity, and superficial CO2 velocity predicted for the axis of the extraction vessel (eo and Uo, respectively). Literature correlations predict a value of eo slightly less than e, and value of Uo slightly less than U. The remainder of the CO2 bypassing the vessel along a high porosity region near the vessel wall, containing a small fraction of the loaded substrate.