The firm has found that the retail price of a one-year-old MINI One or MINI Cooper with an average 8,000 miles on the clock is typically just £200 below its original list price.
Richard Crosthwaite, Glass's specialist car editor, said the car's almost zero depreciation could be attributed to a number of important factors.
'The car has truly captured the public's imagination and has developed a classless appeal for people of all ages,' he said.
'The design of the exterior and interior has been very well received, no doubt aided by the public's affection for the car's innovative predecessor.
'A huge amount of generous press exposure for the way the new MINI drives has also given buyers confidence that there is real substance behind the style.'
He added that there had also been virtually 100% take-up of the tlc service package – offering five years' standard servicing for £100 - so used car buyers know it should cost them little to keep the car in good working order.
He added: 'An additional positive influence on residual values comes from the individuality of the MINIs that are now on the road.
'Used buyers like the fact that it is rare to see two MINIs exactly alike, thanks to the contrasting black or white roof colours of Cooper models and the wide selection of options.'