This paper reports on one phase of a long-term project investigating mathematical content knowledge of pre-service teachers. A cohort of second year PSTs conducted a diagnostic assessment and a series of associated tutoring sessions with a primary aged child. The focus here is on the PSTs' ability to make appropriate task choices following the diagnostic process. Results of the study suggest that PSTs are capable of making sound choices of tasks and associated resources based on their mathematical and pedagogical content knowledge following a targeted diagnostic assessment process.