The delivery of healthcare services at regional level should be modeled on population needs, stemming from patients’ consumption pattern and trying to include unexpressed needs and exclude excesses of demand due to both moral hazard behaviors and inducements from the supply side. We propose a model able to estimate the frequency of access in outpatient care (OC) based on the characteristics of the population. According to empirical evidence, among the determinants of outpatient access we include variables addressing health, socioeconomic status and place of residence, plus variables related to the supply of services. We run generalized linear models for counting data of the Poisson family with the aim of both identifying the determinants of OC utilization and quantifying the related effects. We use the regional administrative database of Basilicata region, year 2019. Results are consistent with literature findings and provide new insights into the analysis of OC, suggesting that our model could easily be implemented by regional policymakers to plan the supply of ambulatory services on population needs.