Abstract:Thyroid hemiagenesis is a rare embryological condition characterized by absence of one of the lobes of the thyroid gland, with the left lobe being absent in 80% of cases and right lobe absent in 20% of cases (a left to right hemi-agenesis ratio of 4:1). We report a case of 25 year old female who presented with right neck mass gradually increasing in size over a period of 2 months. Patient had the history of weight loss and fatigability. The patient work up included an ultrasound neck followed by plain CT neck and contrast CT neck. Ultrasound neck showed absence of left lobe and part of isthmus of the thyroid gland with the right lobe showing features of thyroiditis. These findings were supported by plain and contrast CT neck findings.