This research has tried to study side of the overlap between the financial accounting and the tax accounting, which could cause effects on the results of tax by the measurement accounting acts, this research has studied the impact of the earnings management in companies on the results of tax of these companies, and the impact of the income smoothing, as a special mechanism of the earnings management, on the results of tax, the income smoothing has been studied in this research as the management when smoothes the income it doesn't recognize incomes in the accounting periods itself where there are these profits, but it acts on distribution the income among the years to ease fluctuations in earnings among accounting periods, and thus it avoids large payable taxes in the progressive tax which is compatible with high profits, so that it works to keep profits within the limits of acceptable deductions, but in this research and in the case of the non-progressive Syrian corporation tax which removes the last effect of income smoothing on the Syrian corporation tax, but can be done to take advantage of the process of tax planning to schedule the taxes that are paid among years, therefore this research has tested the relationship between income smoothing and taxable income, and has tested whether there are tax motivations behind the income smoothing, that has been made through testing the relationship between income smoothing with both of "the differences between taxable income and book income" and "the variation in taxable income". The assumed relationships has been tested through testing the hypotheses by using the appropriate statistical methods to the data which are obtained from a sample of companies listed in the Damascus Securities during 2006 to 2012. I found that there is a strong relationship between earnings management and taxable income, but theses earnings are not managed because of tax motivations, and there is a weak relationship between income smoothing and taxable income