Constructive adaptation, a search-based technique for generative reuse in CBR systems for configuration tasks is introduced. We discuss the relation of constructive adaptation (CA) with other reuse approaches and we define CA as a search process in the space of solutions where cases are used in two main phases: hypotheses generation and hypotheses ordering. Later, three different CBR systems using CA for reuse are analyzed: configuring gas treatment plants, generating expressive musical phrases, and configuring component-based software applications. After the three analyses, constructive adaptation is discussed in detail and some conclusions are drawn to close the paper.