In the paper an evaluation's attempt of strong effectiveness of three Pioneer's Open Investment Funds, characterizing by differentiated level of risk, i.e.: Stable Growth Fund, Balanced Growth Fund, Polish Shares Fund, is undertaken. In particular, the first differences of these funds' unit values and WIG20 index, as well as the average profitability of 52 weeks Treasury bill monthly series, relating to the period from January 2001 to May 2007, are used in the empirical studies. Various types of structural breaks, including outliers, observed in the considered time series, are taken into account in the analysis. The Sharpe, Jensen and Treynor-Mazuy models, the Sharpe, Jensen and Treynor ratios, and also some modifications of these tools were applied.