Recently the Journal of Mountain Science published three papers(Lumbres et al.2014;Jung et al.2015;Lumbres et al.2016)that compared selected taper models for bias and precision when estimating upper stem diameters for various tree species.The purpose of this commentary is to point out the consequences of the choice of the variable to be predicted when fitting taper equations and Recently the Journal of Mountain Science published three papers (Lumbres et al. 2014; Jung et al. 2015; Lumbres et al. 2016) that compared selected taper models for bias and precision when estimated upper stem diameters for various tree species. The purpose of this commentary is to point out the consequences of the choice of the variable to be predicted when fitting taper equations and