In this paper we analyse the decision of firms in the Canadian manufacturing sectorto co-operate on innovation projects. Our focus is on the motives behind this decisionand the firm characteristics, both general and with respect to innovation activities,which influence the motives for innovation co-operation. Using data from theCanadian Survey of Innovation 2005 we find that the factors influencing the decisionto co-operate in order to access external knowledge are very similar to thoseinfluencing cost-sharing motives. We also show that public funding leads firms to cooperatein order to access external knowledge and R&D.