A note on a variant of radial measure capable of dealing with negative inputs and outputs in DEA

•Variants of the radial model (VRM) by Cheng et al. (2013) need qualification.•These VRM maintain proportionality only under certain conditions.•This qualified result is based on an earlier, more general analysis. The recent contribution by Cheng et al. (2013) presents a variant of the traditional radial input- and output-oriented efficiency measures whereby original values are replaced with absolute values. This comment spells out that this article contains some imprecisions and therefore presents some further results.