Growing population aging is accompanied by a growing fear of suffering dementia. Four hundred and thirty-six Mexican and Colombian adults completed a survey about their opinion on Medical Assistance in Dying (MAID) for patients with dementia, both in the early stage of the disease and in the advanced stage through an advance directive. In Colombia, MAID is allowed while in Mexico it is banned. The main reasons given by those who agreed with MAID were "right to decide" and "avoiding suffering." Religious beliefs were the main reason for disagreeing. More Mexicans than Colombians agreed with MAID possibly because Mexicans showed a lower degree of religiosity, and also possibly because there are religious movements against euthanasia in Colombia. The results were discussed considering the current debate about MAID in cases of dementia in general, and about requesting it through an advance directive for patients in the advanced stage of the disease.