Match ends, Aberdeen 4, St Johnstone 0.
Jonny Hayes scored twice at Tynecastle as Aberdeen brushed St Johnstone aside to reach the League Cup final.
The little winger converted from close range after three minutes.
The Dons then needed to defend stoutly to preserve their lead before the advantage was extended by a composed Peter Pawlett finish.
After the interval, Adam Rooney raced clear to shoot home and Hayes found the net again with a powerful shot as the St Johnstone challenge faded.
The result means a first final in 14 years for the Dons who had the backing of around three quarters of a packed stadium.
The men in red were first to threaten when a sharp shot on the turn from Rooney was tipped over by keeper Stevie Banks.
The veteran goalie was deputising for the suspended Alan Mannus and it was his poor clearance that led to the opening goal.
Rooney gathered the scuffed goal-kick on the right and left Brian Easton behind before rolling a pass beyond a static Steven Anderson for Hayes to slide in and bundle home from close range.
St Johnstone responded with a concerted period of pressure, forcing six first-half corners and pinning the Dons back.
However, Aberdeen defended determinedly, with Mark Reynolds and Andrew Considine impressing at the back for Derek McInnes's side.
Saints did find a way through when Stevie May and Gary McDonald linked and an unwitting assist from Dons skipper Russell Anderson sent Lee Croft scurrying in on goal.
The former Manchester City midfielder hammered in a low, angled shot but keeper Jamie Langfield got the slightest touch on the ball, directing it against the post.
Dave McKay then made a mess of a close-range header and suddenly Saints found themselves two goals behind.
David Wotherspoon was unconvincing when clearing an aimless, deep cross from Hayes and Pawlett gathered the loose ball to drive into the penalty box before slipping a cool finish under Banks.
St Johnstone hit the frame of the goal again early in the second half when a looping header from McKay landed on the junction of post and bar. McDonald helped the stray ball on and May's attempt to convert from inside the six yard box was thwarted by Reynolds.
Aberdeen thought they had won a penalty when Banks flapped at the heels of Rooney after beating away a low shot from Pawlett but the keeper was spared, briefly, when an offside decision went against the striker.
Rooney was not to be denied, however, and moments later the January signing was celebrating his second goal in two games for the Dons.
Pawlett robbed the dithering McKay and clipped a lovely pass forward for the striker to run on to and slam a shot beyond the exposed Banks.
Saints' heads dropped in the heavy Edinburgh rain as Hayes fired a rising strike over the crossbar and a powerful header from Considine cannoned off the crossbar.
With 10 minutes remaining, Hayes twisted away from the retreating Anderson to send a skidding shot past Banks from the edge of the penalty box and the singing from the jubilant fans in red reached new levels in spite of the wretched weather.
- 5ConsidineBooked at 86mins
- 4AndersonSubstituted forTateat 81'minutes
- 16PawlettSubstituted forLowat 87'minutes
- 15RobsonBooked at 19minsSubstituted forVernonat 82'minutes
- 24EastonSubstituted forMillerat 88'minutes
- 10WotherspoonBooked at 71mins
- 22CroftSubstituted forO'Halloranat 72'minutes
- 11HasselbainkSubstituted forIwelumoat 61'minutes
- Bobby Madden
- Shots on Target
Second Half ends, Aberdeen 4, St Johnstone 0.
Foul by Nicky Low (Aberdeen).
David Wotherspoon (St Johnstone) wins a free kick in the defensive half.
Substitution, St Johnstone. Gary Miller replaces Brian Easton.
Andrew Considine (Aberdeen) wins a free kick in the defensive half.
Foul by Chris Iwelumo (St Johnstone).
Substitution, Aberdeen. Nicky Low replaces Peter Pawlett because of an injury.
Andrew Considine (Aberdeen) is shown the yellow card.
Foul by Andrew Considine (Aberdeen).
Chris Millar (St Johnstone) wins a free kick in the defensive half.
Niall McGinn (Aberdeen) wins a free kick on the left wing.
Foul by Michael O'Halloran (St Johnstone).
Substitution, Aberdeen. Scott Vernon replaces Barry Robson.
Substitution, Aberdeen. Alan Tate replaces Russell Anderson.
Goal! Aberdeen 4, St Johnstone 0. Jonathan Hayes (Aberdeen) left footed shot from the left side of the box to the bottom left corner.
Corner, St Johnstone. Conceded by Andrew Considine.
Substitution, St Johnstone. Michael O'Halloran replaces Lee Croft.
Andrew Considine (Aberdeen) hits the bar with a header from the left side of the six yard box.
David Wotherspoon (St Johnstone) is shown the yellow card.