Optical coherence tomography (OCT) provides more parameters than pure morphology does. In a recent paper [A. Knuettel and M. Boehlau-Godau, J. Biomed. Opt. 5(1) 83–92 (2000)] we have shown that the refractive index (RI) can be evaluated in a localized manner in skin tissue under in vivo conditions. Based on a theory, originally developed for light detecting and ranging applications [L. Thrane et al. , J. Opt. Soc. Am. A 17(3) 484–490 (2000)], the parameter mean scattering angle (MSA) could be derived in addition to RI. The effects of hydration on MSA and RI have been evaluated in vitro in pigskin and in vivo in human skin with our OCT scanner SkinDex 300®. These parameters may have a viable impact in (cosmetic) skin research and clinical diagnoses. To the best of our knowledge, this is the first time that (multiple) scattering of light has been quantified through the observation of a new scattering parameter under in vivo conditions. © 2004 Society of Photo-Optical Instrumentation Engineers.