In this paper, we study empirically the relations between financial constraints and dividend smoothing of firms listed on Korea Securities Market and Kosdaq Market of Korea Exchange. The main results of this study can be summarized as follows. Determinants suggested by the major theories of dividends, namely, residual dividend, dividend signaling, agency, catering, transactions cost theory explain significantly the dividend payout policy of Korea firms. Lintner's dividend adjustment model of dividend policy indicates that firms have long run target payout ratio, and that firms adjust partially about 62.1% of the gap between actual and target payout ratio each year. The estimated dividend adjustment speed is 0.621, and 0.379 of past DPS's regression coefficient is large more than 0.063 of current EPS's regression coefficient. Dividend adjustment speed of past DPS has more effect than dividend adjustment speed of current DPS. These results suggest evidence that Korea firms maintain stable dividend policy which maintain past DPS level without corporate special reason. For considering determinants suggested by residual dividend, dividend signaling, agency, catering, and transactions cost theory to expand Lintner's dividend adjustment model, target payout ratio increase from 0.101 to 0.104, and dividend adjustment speed decrease from 0.621 to 0.442. Therefore, Lintner's dividend adjustment model has the significant estimate on dividend adjustment speed. Dividend smoothing effects change with capital market accessibility. Dividend adjustment speed of capital market accessibility firm is more fast than that of capital market inaccessibility firm, and dividend smoothing effect also change with credit level. Dividend adjustment speed of high credit level firm is more fast than that of low credit level firm. Capital market accessibility and high credit level firm can finance easily in capital markets. Conclusively, past DPS and current EPS suggested by the Lintner's partial adjustment model of dividend policy explain mainly dividend adjustment speed, but financial constraints explain also partially dividend adjustment speed in Korea firms. However, this paper is only early study of the relations between financial constraints and dividend smoothing. It is necessary to expand sample firms and use more elaborate analysis methods.