Optical coherence tomography (OCT) is a new imaging method with promising results for several dermatological indications, including preoperative skin tumour characterization. While high-frequency ultrasound (HFUS) is frequently used for this purpose, overestimation of tumour thickness is a problem, due to subtumoral inflammatory infiltration that cannot be differentiated from tumour tissue. The aim of this single-centre study was to describe OCT features of basal cell carcinoma (BCC) and to determine vertical tumour thickness accurately, including a comparison with HFUS and histopathology. Tumour thickness values of 10 BCCs measured by OCT did not differ significantly from those measured by histopathology (median difference 0.12 mm). By contrast, the difference between HFUS and histopathology was greater (median difference 0.3 mm). A Pearson's correlation coefficient of 0.83 showed a stronger correlation of OCT in measuring tumour thickness compared with HFUS (0.59). Bland-Altman plots revealed a better agreement of OCT and histopathology concerning tumour thickness measurements. On the basis of this explorative study cohort, OCt was more exact than HFUS in preoperative tumour thickness estimation of BCCs compared with histopathological measurements.