This work investigates the saturation pressure of crude oil CO2 mixtures and how the oil plus-fraction characterization methods affect it. Different distribution functions were tested to split the plus-fraction as well as correlations to calculate the critical parameters and the acentric factor. The Soave-Redlich-Kwong (SRK) equation of state was used to calculate the saturation pressure of the crude oil and its mixtures with pure and impure CO2. The results were compared with experimental data and reveal that the effect of the characterization methods on the modeling of the saturation pressure of reservoir fluids is strong mainly for CO2 molar fraction values higher than 50%.