Jamie Heaslip goes over for his second try at Donnybrook
Leinster: (10) 44
Tries: Heaslip 2, Brown, Lewis, Keogh
Cons: Contepomi 5
Pens: Contepomi 3
Scarlets: (15) 34
Tries: Stoddart, King, Stuart-Smith, James, Davies
Cons: Thomas, Davies 2
Leinster moved to the top of the Magners League after staging a superb comeback at Donnybrook on Friday night.
The Scarlets, who secured a bonus point, led 20-10 early in the second half before Leinster scored four tries in a devastating 10-minute spell.
Jamie Heaslip bagged two tries while Gary Brown, Kieran Lewis and Stephen Keogh also touched down for the hosts.
Morgan Stoddart, Regan King, Clive Stuart-Smith, Dafydd James and Barry Davies went over for the visitors.
Leinster were without the bulk of their Irish international but still managed to chalk up a 17th straight home victory.
The Scarlets hit the front in the third minute when Ceiron Thomas slotted over an easy penalty, and making use of an error-strewn start from the hosts, the visitors scored a sublime team try in the 14th minute.
Prop Iestyn Thomas displayed his deceptive pace in midfield and seven passes later, full-back Stoddart managed to slalom over in the left corner.
Leinster slowly mounted their comeback - an offside from Scott Macleod gave them the perfect chance to strike back.
Felipe Contepomi kicked to touch, Bernard Jackman's line-out throw was recycled through the forwards and then shipped out to the left for lurking number eight Heaslip to touch down.
Contepomi's conversion made it 8-7 and although the Argentine added a penalty, the Scarlets took a 15-10 lead into the break thanks to a converted King try.
The New Zealander, who effortlessly pulled the strings in the first half, slipped through a tackle from Luke Fitzgerald to dance over on 32 minutes.
Thomas watched a 28-metre penalty bounce back off the post minutes before the interval, and he almost squirmed over for a try four minutes into the second half.
However, his half-back partner Stuart-Smith succeeded in dotting down off the next phase to push the visitors 20-10 ahead.
But with Owen Finegan and Christian Warner, whose introduction forced man of the match Contepomi to inside centre, impressing off the bench, Leinster turned the game on its head.
A Contepomi penalty was followed up by a 58th-minute try from pacy winger Brown, which brought the sides level.
Then Lewis shrugged off a Barry Davies tackle to romp over on a 40-metre run. Keogh ended a great spell of pressure to dive over from close range and Heaslip followed suit, on 68 minutes, for his fifth try of the league season.
Contepomi, who burst through the league's 500-point barrier, managed to convert all four tries for an incredible scoreline of 44-20.
There was still time for another Contepomi penalty and for King to spark the stunned Scarlets to a late bonus point as James and Davies both crossed the line.
Leinster: R McCarron; G Brown, K Lewis, M Berne, L Fitzgerald; F Contepomi, G Easterby; S Wright, B Jackman, W Green; T Hogan, C Jowitt; S Keogh, K Gleeson, J Heaslip.
Replacements: R Corrigan, B Blaney, O Finegan, D Toner/K McLaughlin, C Whitaker, C Warner/J Sexton, N Ronan.
Scarlets: Morgan Stoddart; Dafydd James, Regan King, Matthew Watkins, Darren Daniel; Ceiron Thomas, Clive Stuart-Smith; Iestyn Thomas, Ken Owens, Craig Dunlea, Vernon Cooper, Scott MacLeod, Dafydd Jones, James Bater (capt), Nathan Thomas.
Replacements: Deacon Manu, Aled Gravelle, Adam Jones, Inoke Afeaki, Liam Davies, Barry Davies, Garan Evans.
Referee: Malcolm Changleng (Scotland).