Jean DOLBEAULT, Maria J. ESTEBAN, Gabriella TARANTELLO Weighted Moser-Trudinger and Hardy-Sobolev inequalities]{A weighted Moser-Trudinger inequality and its relation to the Caffarelli-Kohn- Nirenberg inequalities in two space dimensions. (1283K, Postscript) ABSTRACT. We first prove a weighted inequality of Moser-Trudinger type depending on a parameter, in the two-dimensional Euclidean space. The inequality holds for radial functions if the parameter is larger than $-1$. Without symmetry assumption, it holds if and only if the parameter is in the interval $(-1,0]$. The inequality gives us some insight on the symmetry breaking phenomenon for the extremal functions of the Hardy-Sobolev inequality, as established by Caffarelli-Kohn-Nirenberg, in two space dimensions. In fact, for suitable sets of parameters (asymptotically sharp) we prove symmetry or symmetry breaking by means of a blow-up method. In this way, the weighted Moser-Trudinger inequality appears as a limit case of the Hardy-Sobolev inequality.