To promote consumers' pro-environmental behavior, scenario analysis by life-cycle assessment was applied to drinking water usage, the environmental consequences of which depend on usage behavior. First, elements that characterize drinking water usage were listed, and incompatible elements were grouped into five stages: production and distribution of drinking water, water quality improvement/sales of drinking water, storage of drinking water, use of drink containers, and disposal of plastic bottles. The usage of drinking water was described from consumers' viewpoints, and each scenario was identified by selecting a single element as a module from each of the five stages and then combining the modules. Then, greenhouse gas emissions were evaluated with regard to five types of drinking water (i.e., tap water, small and large containers of domestic bottled water, and small and large containers of imported bottled water) and three types of drink containers (i.e., drinking glasses, water flasks, and plastic bottles). Greenhouse gas emission for each module was formulated as a function of the volume of drinking water, then that in a given scenario for a given volume of drinking water became calculable. Greenhouse gas emissions were compared among scenarios consistent with particular situations or tastes of consumers.