In their recent paper De Marco et al. (2014) concluded that the Loibl function is inadequate to accurately predict AOT40 from biweekly passive ozone sampling in Italy as done in the past, and multivariate, non-linear regression models worked better. Here we demonstrate that their application of the Loibl function is largely inconsistent with previous work, and their GRM functions suffer from ambiguity and cannot be considered valid for inhomegeneous terrain. As such, GRM functions are not proven to be significantly better than the methodology based on the Loibl function, when the latter is properly applied. Further, the new functions by De Marco et al. (2014) were not able to provide hourly estimate of ozone concentrations an important advantage offered by the Loibl function.