Advances in biomedical engineering enable us to treat increasingly severe conditions. This implies an increased need for regulation and priority setting in healthcare, to ensure appropriate safety cautions and to avoid accelerating expenditures. This interview study investigates the mechanisms behind the adoption and use of medical devices through the subjective experiences of hospital staff working with devices for neonatal intensive care. The adoption was found to be primarily initiated by vendor activities, but professionals preferably sought information about functionality from close colleagues. Full integration of devices was sometimes not achieved, and even though the adopting units had good introduction routines, there was no systematic follow-up of how adopted devices had been integrated in the work practices. Diffusion variations were, however, mainly found for temporarily tested devices and not for permanently available technologies. Three factors were found to be the major explanatory variables of the adoption of medical devices: (1) the subjective expected value of the device, (2) information and learning, and (3) the innovativeness of the adopting unit.