For private investors who use foreign capital investments to diversify their assets, the question of income taxation on their investments arises. This study addresses the tax treatment of cross-border investment forms from the perspective of a private investor subject to unlimited tax liability in Germany. On one hand, it presents tax risks such as double taxation of income and the methods to avoid or mitigate them; on the other hand, it explains tax opportunities in the form of lower taxation of foreign investments compared to domestic equivalents. The investigation considers both the current tax legal situation for the assessment period 2008 and the future legal situation - keyword "flat tax" - starting from the assessment period 2009. Additionally, a model is provided.