This paper deals with the modification of the surface properties of expanded polypropylene (EPP). EPP is a semi-hard to soft elastic thermoplastic foam. Because of its special properties, e.g. the rebound resilience at lowest weight, it stands to reason to use EPP also as multifunctional exposed parts for automobile interiors. However, this is due to the very technically seeming surface of typical foam-moldings often not feasible - therefore it is necessary to optimize the surface. The characteristic surface of EPP shows process-related steam nozzle imprints and gussets. Therefore EPP does not satisfy the quality requirements for visible automotive applications. In order to meet these demands, plastic surfaces are usually enhanced with functional or decorative coatings, e.g. textiles, plastic films or paint. The coating of plastics with low surface energies such as PP often leads to adhesion problems by reason of the missing polar and functional groups. This paper gives an evaluation of activation and pre-treatment methods of EPP, with the aim to identify the most suitable pre-treatment method. For this purpose five typical surface treatment methods - flame treatment, corona, fluorination, atmospheric and low-pressure plasma - were performed on EPP samples. As a comparison criterion the maximum increase in the adhesion force between a polyurethane-based coating and the modified EPP substrate was selected. Moreover the influence of the selected pre-treatment method on the increase in the total surface energy and its polar component was investigated by the drop shape analysis method. The results showed that the contact angle measurement is a suitable method to determine the polar and disperse fractions of the surface tension of EPP. Furthermore, all performed methods increased the adhesion of EPP. The highest increase in surface polarity and with that the coating adhesion could be achieved with fluorination. The mechanical evaluation by pull-off-strength tests showed a thirteen-fold increase by fluorination compared to untreated EPP, (0.47 N/mm²(treated) vs. 0.037 N/mm² (neat). With these results the requirements in the car interior (0.3 N/mm²) were exceeded.