This paper presents and analyses integration as a project management concept in industrial system deliveries. Attention is given to the aspect of integrating products and services as a functional whole, i.e. a solution. The study is based on interviews regarding the commissioning process in a number of different project companies. Commissioning is well representing integration as it is the part of the project life-cycle where earlier integration efforts are put into action, and can therefore be evaluated. Combining a literature review with our empirical observations we stress the importance of integration by managing and utilizing relationships throughout the project life-cycle. The outcome of the paper is a framework pinpointing the technical and social dimensions of integration.