To investigate the shielding effects of full-face mask respirators and the suitable positioning of lens dosemeters, irradiation experiments of 90Sr+90Y beta particles were performed using an anthropomorphic head phantom into the eyes of which small thermoluminescence dosemeters (TLDs) were loaded, and the lens doses measured by these TLDs were compared with the doses measured by commercially available personal dosemeters attached around the eyes of the phantom. The three tested masks reduced the beta lens dose to 9-14% as compared to the lens doses in the absence of a mask. As for the suitable positioning of lens dosemeters, the Hp(0.07) evaluated by the Hp(0.07) dosemeter attached at the center of the forehead gave an over-response to the lens dose by a factor of 2.5-8.4 regardless of the presence of masks. The Hp(3) evaluated by the Hp(3) dosemeters, even though placed at extreme positions near the outside corners of the eyes, provided better lens dose estimates with a response of 0.38-1.7, which suggests the potential for improved results when Hp(3) dosemeters are placed at the center of the forehead.