This paper deals with the question how seasonal dummies influence the estimation of the lag distribution. It concerns mainly the Shiller estimator and only partly the Almon estimator. A result of Lovell for the case of estimation under linear restrivtions is used, since the Shiller estimator satisfies the corresponding conditions. The connection between the Shiller and the Almon estimator is shown. the influence of the “maximum lag” which the user fixes is examined for both approaches “with” and “without” seasonal dummies.