AbstractIn many countries, health insurers or health plans choose to contract either with any willing providers or with preferred providers. We compare these mechanisms when two medical services are imperfect substitutes in demand and are supplied by two different firms. In both cases, the reimbursement is higher when patients select the in‐network provider(s). We show that these mechanisms yield lower prices, lower providers' and insurer's profits, and lower expense than in the uniform‐reimbursement case. Whatever the degree of product differentiation, a not‐for‐profit insurer should prefer selective contracting and select a reimbursement such that the out‐of‐pocket expense is null. Although all providers join the network under any‐willing‐provider contracting in the absence of third‐party payment, an asymmetric equilibrium may exist when this billing arrangement is implemented.