Enterprise Resource Planning (ERP) systems have reached a high level of maturity, and maintenance and improvement of implemented systems is becoming increasingly important. This paper proposes to analyze the ERP maintenance problem along three interrelated dimensions: software maintenance (SM), business process management (BPM) and process improvement (PI). It is argued that BPM and PI practices facilitate maintenance of ERP systems. The proposed analysis framework is applied to study maintenance of the ERP system at a large energy company. The analysis suggests that relatively high level of maturity has been achieved in corrective and adaptive maintenance. However, the level of maturity is lower in perfective and preventive maintenance, and links between maintenance of the ERP system and BPM should be improved.