Purpose – Health policy-makers are increasingly promoting programs that embed cost-opportunity logics. Their implementation requires the mobilization and exploitation of expert knowledge controlled by professionals dispersed in the territory, unaccustomed to share/integrate their knowledge with others, and sometimes adversary to cost-opportunity logics. The success and viability of these programs thus depends on experts’ commitment to mobilize and integrate their knowledge. Past studies highlight reasons why policy might not be able to stimulate change because of institutional forces that hinder knowledge mobilization and professionals’ micro-processes and narratives that oppose new practices that alter their autonomy or their routines. The present study investigates if and how policy-makers can pursue a strategic change in their eco-system. Methodology – We investigated the case of a new Health Technology Assessment (HTA) program in Lombardy. Our unit of analysis relates to the strategy implemented by Region Lombardy to implement the HTA program. We triangulated data from: (i) archival analysis of normative and documents; (ii) quantitative analyses measuring experts’ participation in program, etc.; (iii) presentations and web reports; (iv) direct interviews with key informants; (v) participant observations of meetings and workgroups. Interviews involved the regional staff implementing the HTA program and a panel of 28 experts involved in its application. Originality/value – Our study highlights the contribution of learning mechanisms on professionals’ commitment to the new practice. The strategy implemented by Region focused upon professionals’ learning and relied on three mechanisms: (i) cognitive mechanisms supporting learning through common language, frameworks and values; (ii) structural mechanisms supporting learning with inter-organizational infrastructures; (iii) procedural mechanisms supporting learning through methods and tools that institutionalized the new practice. The interplay of learning mechanisms was not sufficient to achieve the full-fledged diffusion of the practice in the territory, but ‘only’ to disrupt indifferences locally, and stimulate early HTA experiences that added up to the gradual legitimization of the practice. Practical implications – Our analysis provides indications to policy-makers regarding the relevance and limitations of strategy of change entirely focused on learning mechanisms. It highlights the interplay of OLMs in creating an understanding of the change (instrumental for motivating individuals to engage in it) as well as a proper context, made of norms and infrastructures that are instrumental for allowing individuals the practical opportunity to mobilize and implement their knowledge.