The heads of R&D departments are those most responsible for the adaptation of firms' human resource management (HRM) practices to the idiosyncrasies of their departments. From their description, this paper analyzes the HRM practices in R&D departments and the adaptation achieved in four different firms. The data suggest that the main adaptations are produced primarily in recruiting and organizing the work of R&D personnel. In contrast to suggestions in the specialized literature, less adaptation is found in other HRM practices analyzed (managerial support and degree of delegation, compensation and career plans). Psychological theories of procedural justice and social comparison can improve our understanding of such results. The organizational structure affects the reference group for such comparisons and, consequently, the R&D managers' capacity to adapt such practices. Based on these arguments, the delegation of HRM practices to R&D departments will enhance the degree of adaptation of such policies. © 2009 Blackwell Publishing Ltd.