Holdings of money and illiquid assets are likely to be determined jointly. Therefore, frictions that give rise to a need for money may affect capital formation, resulting in either too much or too little investment. Existing models of money and capital however tend to overlook that both types of investment inefficiencies can be equilibrium outcomes. Building upon insights from the New-Monetarist literature, we construct a model in which preference heterogeneity between agents implies that both

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... ver-and under-investment can arise. We use our framework to study whether monetary policy can effectively resolve both types of investment inefficiencies, and find that increasing inflation could resolve under-investment inefficiencies while reducing inflation could curb over-investment inefficiencies. JEL Classification: E22, E41, E44, E52, O16. * We would like to thank Aleksander Berentsen and Francesco Carli for valuable discussions and recommendations on this topic. We also thank seminar participants at Tilburg University and the University of Basel. †