Given the rising role of users in innovaton processes and the increasing amount of research in this feld the aim of this paper is to explore the limits of our understanding of the user innovaton (UI) concept. In doing so, the study addresses four basic questons: (1) Why do users create and share innovaton? (2) Who is the userinnovator? (3) What type of innovaton do users create? (4) How do users innovate? The results of a systematc literature review identfed the main research streams on user innovaton, together with weaknesses of past research and perspectves for future studies.