We show that important layer parameters of the double barrier active region in semimagnetic II-VI semiconductor resonant tunneling diodes (RTDs) can be accurately determined from high-resolution Xray diffraction (HR-XRD) scans of complete structures. This is remarkable, since the scattering volume of the typically only few nm thin double barrier region is low compared to the thick, complex contact and buffer layers it is embedded in. The parameters obtained by HR-XRD of several RTD structures are correlated with current-voltage characteristics, finding good agreement with the expected exponential dependence of the off-resonance tunneling current on the measured barrier thickness and height. Thus direct and nondestructive determination and optimization of the active region properties are possible for such II-VI spintronic devices. (C) 2010 Elsevier B.V. All rights reserved.