In the truck industry there is a continuous demand to increase the efficiency and to decrease the emissions. To acknowledge both these issues a waste heat recovery system (WHR) is combined with a partially premixed combustion (PPC) engine to deliver an efficient engine system. Over the past decades numerous attempts to increase the thermal efficiency of the diesel engine has been made. One such attempt is the PPC concept that has demonstrated potential for substantially increased thermal efficiency combined with much reduced emission levels.So far most work on increasing engine efficiency has been focused on improving the thermal efficiency of the engine while WHR, which has an excellent potential for another 1-5 % fuel consumption reduction, has not been researched that much yet. In this paper a WHR system using a Rankine cycle has been developed in a modeling environment using IPSEpro.A comparative investigation of the WHR potential between the existing conventional diesel combustion and the novel PPC combustion is done. Even though the PPC is a low temperature combustion concept (LTC), implying that the exhaust temperatures are lower than for the traditional diesel combustion, the EGR quantity is higher which in total still offers improved WHR potential as that of conventional combustion. The EGR cooler offers higher quality heat when compared to exhaust gas and CAC, hence the WHR potential using only the EGR system is considered in this paper.