%0 Journal Article %T On sumsets of dissociated sets %A I.D. Shkredov %J Online Journal of Analytic Combinatorics %D 2009 %I University of Auckland %X In the paper we are studying some properties of subsets $Q subset Lambda_1+,,,+Lambda_k$, where $Lambda_i$ are dissociated sets. The exact upper bound for the number of solutions of the following equation $q_1 +,,,+q_p =q_{p+1} +dots+q_{2p}, q_i in Q~~~~~ (1)$ in groups $mathbb F_n^2$ is found. Using our approach, we easily prove a recent result of J. Bourgain on sets of large exponential sums and obtain a tiny improvement of his theorem. Besides an inverse problem is considered in the article. Let $Q$ be a set belonging to a sumset of two dissociated sets such that equation $(1)$ has many solutions. We prove that in the case the large proportion of $Q$ is highly structured. %U http://analytic-combinatorics.org/index.php/ojac/article/view/56