Would the same person invest differently depending on the investment purpose? Using Danish administrative data linking parents and children, we compare adults who manage both a personal brokerage account and their child’s account. Exploiting within-family variation, we show that child-labeled accounts contain safer, more diversified portfolios, trade less, and have a weaker disposition effect, yielding higher Sharpe ratios despite lower expected returns. Parents' personal accounts take more systematic and idiosyncratic risk, tilting toward foreign and lottery stocks. These within-investor differences reconcile active behavior in brokerage data with the inertia documented in 401(k)s, suggesting that the gap reflects mental accounting.