The crystal structure of cannabidiol, C21H30O2, {systematic name: 2-[(1R,6R)-3-methyl-6-(prop-1-en-2-yl)cyclo­hex-2-en­yl]-5-pentyl­benzene-1,3-diol}, was determined earlier by Jones et al. [(1977). Acta Cryst. B33, 3211–3214] and Ottersen & Rosenqvist [(1977). Acta Chem. Scand. B31, 749–755]. In both investigations, the absolute configuration is given as R,R, referring to Mechoulam et al. [(1967.J. Am. Chem. Soc. 89, 4552–4554]. In the latter, the absolute configuration was identified by chemical means. Using the advantages of modern single-crystal X-ray diffractometers such as area detectors and high-intensity radiation sources, a high-quality structure determination including the absolute configuration was possible and is shown in this work. Furthermore, the rather uncommon Cu Kβ wavelength radiation was applied for the structure determination, which confirmed the absolute structure to be R,R.