We report on the synthesis and structural characterization of six novel arylarsonate-containing polyoxomolybdates with fluorinated-functionalities in the para position of the phenyl ring. The reaction of the various arylarsonic acids, RAsO3H2 [R = 4-F-C6H4 (H2LF), 4-F3C-C6H4 (H2LCF3), 4-F3CO-C6H4 (H2LOCF3)] with Na2MoO4·2H2O in aqueous pH 3 solution resulted in the heteropoly-6-molybdates [{(4-F-C6H4)As}2Mo6O24(H2O)]4- (1), [{(4-F3C-C6H4)As}2Mo6O24]4- (2) and [{(4-F3CO-C6H4)As}2Mo6O24(H2O)]4- (3), which were isolated as guanidinium salts. When the reaction was performed in aqueous pH 1 solution the inverted-Keggin type heteropoly-12-molydates [{(4-F-C6H4)As}4Mo12O46]4- (4), [{(4-F3C-C6H4)As}4Mo12O46]4- (5) and [{(4-F3CO-C6H4)As}4Mo12O46]4- (6), were obtained and isolated as sodium salts. The 6-molybdates 1-3 and the 12-molybdates 4-6 can be easily interconverted reversibly in solution as a function of pH (3 vs 1). Polyanions 1 and 3 are isostructural and they exhibit a bent hexamolybdate ring, whereas the ring is flat for 2. The inverted-Keggin polyanions 4-6 are isostructural and the metal-oxo core is capped by four arylarsonate groups. All six polyanions have been characterized in the solid state by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, and hermogravimetric analysis as well as in solution by multinuclear NMR (1H, 19F). The synthetic procedures for the arsonic acids (4-F3C-C6H4)AsO3H2 (H2LCF3) and (4-F3CO-C6H4)AsO3H2 (H2LOCF3) are reported for the first time.