In this article we use a comparative case study of collaborative research centres that operate at the interface between public science and private industry to question the assumption that hybrid organizations lead to hybrid practices. Public–private partnerships are intended to contribute to new work practices that solve challenges in public service provision and influence industrial innovativeness by engaging public research capabilities. Analysis of eight Scandinavian centres indicates considerable variance with respect to levels of integration of public and private partners and tensions between them. Five of the cases display no or highly contested hybrid practices and there seem to be many barriers to hybridization. Large differences in work practices from earlier interaction between the partners and radical goals of commercialization of excellent public science are important explanations.