Real Madrid great Ronaldo believes the LaLiga champions should sign Kylian Mbappe ahead of Paris Saint-Germain team-mate Neymar.
Mbappe has been tipped to make the move to Madrid at some stage in his career, with Los Blancos reportedly eyeing a 2021 transfer.
Former Barcelona forward Neymar – who joined PSG in a world-record €222million deal in 2017 – has also been linked to Madrid previously.
But Brazilian legend Ronaldo, a LaLiga winner with Madrid in 2002-03, prefers France's Mbappe over countryman Neymar due to age.
"Right now, it is not that one is better than another, but if Real Madrid had to make a big investment, they should do so thinking about the future," Ronaldo said during a webinar hosted by Santander.
"Neymar is 28 years old and Mbappe is 22.
"As an investment, it would be more logical to bring the younger [of the two]."
Mbappe and Neymar are preparing for Sunday's Champions League final against Bayern Munich in Lisbon.
French powerhouse PSG will feature in their first Champions League decider, having dominated domestically.
Neymar – who won the 2015 Champions League with Barca – and PSG have already claimed Ligue 1, Coupe de France, Coupe de la Ligue and Trophee des Champions in 2019-20.
"He needs to win the Champions League to complete his season," Ronaldo said of Neymar.
"He has played very well in the last few games, especially in this final phase in Portugal.
"He has created many scoring chances, but he has lacked calmness to finish off moves. With luck and calmness, he can find himself scoring in the final."