Purpose -The purpose of this paper is to establish a model to study the determinants of financial flows, portfolio and foreign direct investment (FDI) flows, and the impact of these determinants on economic variables in samples of developing and advanced countries. The analysis then turns to an evaluation of the effects of external flows on economic activity. Design/methodology/approach -To that end, the paper follows a two-step procedure. First, the paper estimates a series of reduced-form equations in differenced form, using annual data, for the current and the financial account balances as well as important underlying components, using a number of macroeconomic indicators reflecting the state of the business cycle as explanatory variables. These include not only a measure of economic growth, but also other factors that vary cyclically, such as the exchange rate and energy prices. In addition, the paper examines the effect of positive and negative shocks to these and other cyclical variables on components of the balance of payments. Second, the results are summarized in three directions. First, cross-country correlations evaluate time-series co-movements between the current account balance and external flows with respect to major determinants of cyclicality across the samples of advanced and developing countries. Second, time-series regressions evaluate the direct effects of financial flows on the current account balance within the samples of developing and advanced countries. Third, cross-country regressions evaluate the impact of movements in trend and variability of financial flows on major economic indicators across the samples of developing and advanced countries. Findings -The results are summarized in three directions. Across the samples of advanced and developing countries, the pervasive evidence highlights the negative correlation between the responses of the current account balance and the financial balance with respect to the various sources of cyclicality in the time-series model. Second, using time-series regressions the bulk of the evidence indicates that an increase in financial flows helps finance a widening current account deficit. Third, cross-country regressions evaluate the impact of movements in trend and variability of financial flows on major economic indicators across the samples of developing and advanced countries. While FDI flows appear significant in differentiating growth performance within and across developing countries, their effects appear to be limited on growth performance in advanced countries. Portfolio flows are more relevant, compared to FDI flows, to financing a wider current account deficit, both in developing and advanced countries. Originality/value -Overall, the evidence presented in this paper establishes the importance of financial flows to external balances and macroeconomic performance within and across the samples of developing and advanced countries. In light of this evidence, macroeconomic policies should target a combination of external balances that can be ea...