With Max Barry and Kieran Shanks both suspended, Barry Robson gave Jack MacIver and Duncan their first starts of the season as his team looked to maintain the pressure on Rangers at the top of the table.
Lyall Booth supplied the ammunition for Aberdeen's first couple of chances as Michael Dangana and Kieran Ngwenya got on the end of the full back's crosses to force saves from Irvine in the opening ten minutes.
The ever dangerous Kevin Hanratty tried his luck from distance but lifted his shot too high before Jack MacIver forced another save from Irvine as Aberdeen dominated the opening exchanges.
Inverness full back Nicolson fired a dangerous ball into the home box, but Kyle Dalling was well-placed to clear the danger. It had been an open and entertaining opening quarter of an hour despite a blustery, bitterly cold wind.
In the nineteenth minute a long ball from MacIver found Dangana who turned two defenders before racing into the box where he was pulled down by Thain -a clear penalty. Connor Barron fired the ball low past the right hand of Irvine to give Aberdeen a deserved lead.
Six minutes later Cairns tested Ritchie from distance but the Dons number one made a comfortable save. Moments later a huge scramble in the Aberdeen area saw Barron hack the ball off the line to deprive the Highlanders an equaliser.
On 32 minutes the Dons doubled their advantage. Ryan Duncan played a neat one-two with Dangana before firing the ball into the net from fifteen yards - his first Under 18 goal of the season.
Ngwenya twice came close just before the break but right on the stroke of half-time Dangana made it 3-0 when he accepted a MacIver pas before beating his man and driving the ball into the bottom left hand corner of the net.
A good first-half showing by Aberdeen who looked comfortable as the interval arrived.
Half time - Aberdeen Under 18s 3 Inverness Caley Thistle Under 18s 0
The visitors, coached by Ryan Esson, were out of the blocks quickly in the second period and pulled a goal back in the 46th minute when left back Nicolson popped up at the back post to knock in McLean's cross from the right.
Inverness enjoyed a good spell after their goal and felt they might have had a penalty on 58 minutes when Gamble went down in the area. Coach Ross Jack carried his protests a little too far for the referee's liking, earning himself a yellow card.
On 62 minutes, Dangana was cautioned for simulation, then two minutes later it was 4-1 for the young Dons. A Barron free-kick from twenty yards was superbly touched on to the post by keeper Irvine only for the ball to rebound to Duncan who had the easiest of tasks to roll the ball into an empty net.
On 67 minutes Thain was booked for a foul on Hanratty, just before winger McLean saw an ambitious volley comfortably saved by Ritchie. To Inverness's credit they kept trying to push forward at every opportunity but the central defence of Dalling and Andy Paterson was proving to be a formidable obstacle.
In the 74th minute a fine run and cross from Calvin Ramsay was finished off by a composed strike from Dangana to notch his second and Aberdeen's fifth goal of the game and put the seal on a solid victory.
Credit to Inverness who continued to pass the ball about well till the very end, but Aberdeen had that quality needed in the final third.
Youngsters Finn Yeats and Andrew Buchan were given a run out before the end as the Dons ran out comfortable victors making it nine wins out of ten in the league to date.
Full time - Aberdeen Under 18s 5 Inverness Caley Thistle Under 18s 1