The Pensión Plans and Pensión funds are a product of saving-forecast with a complex legislative framework in Spain. This way, the law of their specific regulation was approved in 1987. Nevertheless, a multitude of legislative changes have been accomplished, in order to correct certain faults and to give more safety to this product, such as avoiding the double-tax, to submit them to the system of regulation and supervisión of the insurance companies, as well as to favor their development. This paper analyses the following up of their establishment in Spain as well as the diverse legislative changes to which they have been submitted, which explain their slow development in this European country.