Curriculum resources are integral to teaching, yet more could be known about preservice teachers' curricular use when planning mathematics lessons. Framed with a consideration toward teachers' pedagogical design capacity, this study explores the decisions preservice teachers make when presented with four curricular resources and tasked with planning one lesson. Preservice teachers were pressed to provide rationale for their decision making around choice of resources. Findings indicate some resources were used much more extensively than others. The most common reasons cited were appropriate rigor and useful problems. Depending on the resource, the incorporation of manipulatives and real-world connections were also commonly cited.