The radiation dose to the lens of the eye was measured using thermoluminescent dosimeters placed over the eyelids of 82 patients undergoing coronal CT examinations of the sinuses at six CT scanning units in the West of Scotland. The lens doses were dependent upon the mAs setting of the scanner, with a mean lens dose of 70.3 mGy at 475 mAs, 17.6 mGy at 210 mAs and 4.7 mGy at 30 mAs. All coronal CT examinations of the sinuses requested for the planning of functional endoscopic sinus surgery should use a low mAs technique. The mAs setting should be locally agreed between the radiologist and ENT surgeon, depending on their joint assessment of scan quality.