The objective of this paper is to investigate empirically a possible causal relation between capital flows (and financial openess in a widely fashion) and long run economic growth. With a sample of 70 countries in the period ranging from 1970 to 2004 we estimated econometric panels to test for the presence of a productivity growth enhancing effect of higher capital flows. Since the literature points out an assimetric effect in the sense that foreign capital is desirable only for countries which have attained a certain level of absorptive capacity, that means, which are more able to convert them to productive capital, interactive terms were included in the regressions. More specifically, we tested the role of the financial depth, measured as the ratio of domestic private credit over GDP, on the relationship between capital flows and growth. The results obtained show that economies which have already attained a certain ratio of credit over GDP greater than a threshold that varies between 25% and 30% has a positive and significant impact of capital flows on growth. Below this threshold, this impact is negative. Since excessive capital flows exerts a pressure of strong appreciation of the real exchange rate of a country and that appreciation may be negative to productivity growth since it imposes significant losses to tradables sectors, it is possible that countries with a low financial depth had grown less because of the effects of appreciation of the exchange rate caused by capital flows. However, the regression estimates between real exchange rate misalignments and growth show a negative significant effect by a statistical standpoint but insignificant by an economic standpoint.