Nicholson scored two of his goals from the penalty spot
Barry Nicholson netted a hat-trick as Aberdeen brushed Inverness aside to reach the CIS Cup semi-finals.
Derek Young was hacked on nine minutes and Lee Miller was the victim of a bad tackle after 20 minutes, with Nicholson slotting away both penalty awards.
A blunder from keeper Michael Fraser then left Miller with an easy tap-in.
Graham Bayne replied with a 67th minute strike but Nicholson stroked in a close range effort to complete a good night for the home side.
Caley Thistle player-manager Craig Brewster had warned his players not to repeat the sluggish start that marked their recent league defeat to the Dons.
But the visitors failed to heed their manager's advice and gifted Aberdeen two early penalties.
A foul by Richard Hastings on Young was clinically punished from 12 yards by Nicholson.
The midfielder almost created a second goal shortly afterwards when his inswinging free-kick was headed over by the diving Miller.
Stuart McCaffrey then brought down Miller and Nicholson once again confidently placed the ball into the right-hand corner of the net.
Russell Duncan tried to haul the visitors back into contention in the 29th minute with an ambitious half-volley from 30 yards, but the ball flew narrowly wide.
The same player could then only watch on in anguish as Jamie Langfield clawed another powerful strike away from the top corner of the Dons goal.
One the stroke of half-time, Fraser took one touch too many in trying to control a lofted back-pass from Grant Munro and left Miller with a simple finish.
Inverness began the second period in positive fashion and from Ross Tokely's cross on the right-wing, Dennis Wyness planted a firm header straight into the chest of Langfield.
Brewster's men continued to push forward and Barry Wilson had a shot beaten away by Langfield before Wyness cut inside and smashed an effort just over.
The visitors' determination was finally rewarded when Wyness seized on some slack play by the Dons defence and Bayne was on hand to drive the loose ball into the back of the net.
However, it did not take long for Aberdeen to restore their three-goal advantage, as with 12 minutes remaining Nicholson scored the goal from close range which guaranteed him the match ball.
The visitors kept going and substitute Marius Niculae had time to draw a great stop from Langfield through a downward header.
Aberdeen: Langfield, Hart, Diamond, Mair, Byrne, Jamie Smith (Foster 59), Nicholson, McNamara, Aluko (Considine 72), Young (Clark 30), Miller. Subs Not Used: Kelly, Maguire.
Goals: Nicholson 10 pen, 21 pen, Miller 45, Nicholson 78.
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