The author ponders over his long-lasting relations in economic research activities with Zdzislaw Sadowski on the occasion of the 80th birthday anniversary of the latter. In view of the quite different areas of their research he concentrates mainly on comparison of concrete tasks they had to fulfill and the condiions of their realisation. It is only recently that after certain changes in their research fields they entered the way of a direct cooperation, namely on the present state of Kalecki's economic theory, which in fact had been their theoretical background even when they had been previously working in the two different fields of the political economy, those of socialism and capitalism respectively.