This special issue of the Journal of Universal Computer Science on Conceptual Modelling of Services focusses on disseminating the results of innovative research in conceptual modelling addressing standing challenges in the emerging areas of service computing and service-oriented software engineering. The call for papers for this special issue solicited original work devoted to the general question of how the well established conceptual modelling discipline can provide support for the novel and fast growing paradigms of service orientation to meet the challenges of today's software systems engineering.