French vowels /i/ and /y/ were noticed to be less subject to variation on F1/F2 plan compared to the other French vowels [7,11]. Quantal Theory of Speech predicts that these two vowels are focal and thus characterized by the proximity of two of their formants (respectively F2/F3 for /y/ and F3/F4 for /i/). Higher formants values F3 and F4 as well as their amplitude are investigated in this study in order to show that French /i/ and /y/ have more compact F3/F4 and F2/F3 as compared to seven other languages. We also suggest that these higher formants allow better understanding for the variation of these vowels. We underline the importance of F3 measurements to characterize the variations of these vowels, notably due to their difference in rounding.