Patients with thyroid disease have been reported to develop psychiatric symptoms. However, the specific psychological mechanism underlying their development remains unknown. This paper examined the psychological features of patients with thyroid disease using both the Japanese version of the NEO Five-Factor Inventory and the Tree Drawing Test. A total of 64 patients with Graves' disease, 38 with Hashimoto disease, and 68 with Nodule Goiter were examined, and compared with 22 neurotic patients. The following results were obtained: (1) While patients with thyroid disease obtained standard scores on the Japanese version of NEO Five-Factor Inventory, they drew less structured trees regarding boundary compared with the neurotic patients; and (2) patients with Nodular Goiter exhibited more notable weakness of the boundary than patients with Graves' disease. The implications of these results are discussed in comparisons with the levels of psychological adjustment according to objective and projective personality tests.

Key words: Thyroid disease, NEO-FFI, Tree Drawing Test