Spanish publication 'Sport' reports that the Portuguese currently earns £18.6m a year at the Spanish giants, but is looking for a pay rise that will see that figure rise to somewhere in the region of £35.5m.
The aforementioned source claims that Ronaldo has that figure in mind because it is how much Messi earns at the Camp Nou.
Ronaldo is reportedly growing frustrated at the Bernabeu, having yet to be offered the new contract that club president Florentino Perez promised him some time ago.
Widespread reports in Spain claimed that the 32-year-old had been promised a new deal after helping the club to La Liga and Champions League glory last season, but he is still waiting.
Ronlado still has three and a half years to run on his current contract, which he signed in November 2016.