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This paper presents additional developments about a flood frequency approach proposed by Gaume et al. [2010], aiming at incorporating available information on extreme floods at ungauged sites in a regional flood frequency analyse. Extreme floods, indeed, may represent a very large additional record length if compared to gauged series, and therefore may highly improve the accuracy of flood quantiles estimates. However, the proposed approach requires to calibrate an index flood relationship (here an exponent of catchment surface), which complexifies the regional statistical model. The performances and robustness of this approach are tested here and compared to the conventional regionalisation approach of Hosking & Wallis [1997]. The comparison is based both on simulations and on a case study. The inference procedure used is based on a GEV distribution associated with a specific likelihood …