The term arrowroot is used for the starch obtained from the rhizomes of Maranta arundinacea. In the present work effects of 60Co radiation treatment (dose up to 15 kGy) on structural characteristics and pasting properties of arrowroot starch were evaluated. Thermal properties, granule size and shape and size distribution, by means of optical and scanning electron microscopy and Fourier transform IR (FTIR) spectra were also obtained. On pasting properties strong decrease in peak and final viscosities, as well as breakdown, were observed. In the dose range applied, minimal changes in crystallinity, molecular composition and structure of arrowroot starch were found.