These data files are of CT scans of two species of fish (Hill stream loach) collected at The Hounsfield Facility, School of Biosciences, University of Nottingham as part of a collaborative project with Jay Willis and colleagues at University of Oxford. The work is submitted to BioRxiv titled "The structure and function of the sucker systems of hill stream loaches" (2019). The CT image data shows cross section images of Sewellia lineolate (Pseudogastromyzon sp.) and Gastromyzon puntilatus.