We characterize the local O3 production at an urban and a rural site in the northern part of the Po valley (Italy) during the Pianura Padana Produzione di Ozono experiment (PIPAPO). A steady state calculation based on observations is performed to determine the local O3 production rate, P(O3), and its sensitivity to precursor concentrations. The urban site exhibited a strongly VOC sensitive O3 production rate, while both VOC and NOx sensitive conditions were observed at the rural site. In addition to the local steady state analysis, we performed one-dimensional Lagrangian model calculations that simulate conditions in the Po valley. These calculations show that the P(O3) at the surface tends to be more VOC sensitive than the average in the mixed layer. The Lagrangian calculations are also used to determine the response of O3 concentration to an emissions change. We compare emission control information with information on sensitivities from the local analysis. It is concluded that a local analysis of P(O3) within the mixing layer offers useful qualitative information but tends to overestimate VOC sensitivity as judged by a comparison with an emissions-based Lagrangian model.