Résumé: The principal conjecture of mirror symmetry predicts that certain differential equations built from Gromov-Witten invariants will turn out to be geometric, i.e. of Picard-Fuchs type. Thus, a classification problem in algebraic geometry can be translated into a mirror-dual classification problem in DE's. As an illustration, we shall approach a problem that we believe to be mirror dual to the problem of classifying Fano threefolds with one-dimensional Picard lattice (solved first by Iskovskih).