I signed a form with the Church that my parents ashes would be cared for with dignity. Some of my siblings want to spread their ashes in the mountains and favorite beach. I say no as this in not respectful or dignified.
From the USCCB (emphasis added):
The cremated remains of a body should be treated with the same respect given to the human body from which they come. This includes the use of a worthy vessel to contain the ashes, the manner in which they are carried, and the care and attention to appropriate placement and transport, and the final disposition. The cremated remains should be buried in a grave or entombed in a mausoleum or columbarium. The practice of scattering cremated remains on the sea, from the air, or on the ground, or keeping cremated remains on the home of a relative or friend of the deceased are not the reverent disposition that the Church requires. (Order of Christian Funerals, 417)