Individuals tend to simplify a complex portfolio decision problem into several manageable dimensions, each of which can frame their perception of risk. We check this view by studying the effect of investment horizons on households' portfolio decisions. Using the Survey of Consumer Finances (SCF) data, we find that households allocate more of their wealth in stocks if they report longer planning horizons. The existence of foreseeable expenditure significantly changes the dependence of risky stock investment on the planning horizon. We decompose the reported planning horizon into an objective part and a subjective mental accounting part, and find that the mental accounting part has a greater effect on household portfolio choice. This is consistent with the argument that individuals make investment decisions based on the horizon at which the risk is perceived rather than the horizon at which the investment reward or cash is needed. Copyright © 2010 John Wiley & Sons, Ltd.