Rapid technological changes within a highly competitive global market have induced a transformation in the manufacturing industry. A wide range of services is added to the physical product in order to deliver new customized functions and other benefits in the form of Product-Service Systems (PSS). These developments induce a change from quasi-stable and simple socio-technical systems to a more complex and instable dynamic configuration. Various environmental factors also influence the requirements towards the PSS in all life cycle phases. However, such factors have yet to be systematically identified and categorised. Thus, this paper presents the results of a structured literature review on factors influencing the system requirements along the PSS life cycle. The review has classified such factors in three life cycle phases and four categories. Gaps in research have been identified for factors during operation and end of life, especially beyond functional requirements. Thus, future research opportunities have been derived.