Project management is a discipline for effective resource management in order to meet the specific goals of the organization. Organizations usually implement several projects at once, which form a project portfolio. In time, possible projects come in organizations, which are characterized by the required resources and the achievement of the organization's goals. The required resources form the inputs and the achieved level of fulfillment of the organization's goals forms the outputs of the created model. Efficient projects can be then determined using the basic data envelopment analysis (DEA) method. Total resources are available in the organization in limited amounts. A portfolio composed only of effective individual projects may not always provide an effective portfolio due to maximizing overall output with limited resources. The article suggests a new method for project portfolio forming based on a generalized DEA model. The efficiency of the portfolio and the effectiveness of outputs are used as performance measures of the designed project portfolio. Useful extensions of the procedure are considered and analyzed.