Precise powder diffraction data collected with a monochromatic radiation from a conventional X-ray source have revealed the presence of diffraction lines with low intensity not indexed from the unit cell reported for [Y(H2O)](2)(C2O4)(CO3)(2), From powder pattern indexing it has been shown that yttrium oxalate carbonate crystallises with an orthorhombic unit cell with the parameters a = 7.8177(7) Angstrom, b = 14.943(1) Angstrom, c = 9.4845(7) Angstrom, V = 1108.0(1) Angstrom (3), S.G C222(1), Z = 4. This result demonstrates that the c parameter is doubled with respect to the value previously reported. The crystal structure has been solved ab initio from X-ray powder diffraction data and refined by the Rietveld method (R-F = 0.06 and R-wp = 0.12). The yttrium atoms are nine-fold coordinated and the orientation of the carbonate groups alternates in the direction [001], while they had the same orientation in the structure model reported in the literature.