This paper extends the traditional hedonic price specification to take into account the unobserved heterogeneity of sellers, buyers and seller-buyer matches. The specification is estimated using econometric techniques for non-nested panel data models on a data set of nearly 15 million transactions occurring in French wholesale fish markets over the 2002-2007 period. Results show that unobserved heterogeneity plays a significant role in price setting. For some species, its inclusion in price regressions changes the coefficients of quality-related fish characteristics. Fish characteristics are the main factors explaining price variations for many species, but time and buyer effects also play a significant role.