This paper builds an overlapping generations model with gift motivation and use it to study the interaction between consumption externalities and gift motivation, as well as the effects on optimality of the equilibrium path. We find that the operativeness of gift motivation determines the channels of distortion of consumption externalities. When the gift motive is operative, consumption externalities only affect the intratemporal allocation of consumption between the young and the old. The optimal tax policy consists of a tax on gift and a tax on capital income. When the gift motive is inoperative, consumption externalities not only affect the intertemporal allocation of consumption of an individual when young and when old but also modify the path of capital accumulation. The optimal tax policy in this case consists of a tax on capital income and a pay-as-you-go social security system.