Scarlets moved level on points with Pool Five leaders Leicester Tigers on Saturday thanks to a 35-27 bonus-point home victory over Italian side Treviso.
The hosts, who had a scare when outside-half Stephen Jones went off after only 18 minutes with a knee injury, out-scored Treviso four tries to three but could never kill off the Italians, who had the better of the final quarter.
Scarlets went in to the game in the midst of a prop crisis with Deacon Manu, Rhys Thomas and Peter Edwards all out injured.
It meant the west Wales region had to register Wales Under-20 cap Simon Gardiner, who went straight in to the starting line-up .
The match also saw Stephen Jones, who turned 33 this week, and skipper Matthew Rees make their first Scarlets' starts since the side were hammered at Leicester in October.
And it was Jones who helped give the home side a perfect start. He put Lamont through for a converted try after only 87 seconds before putting over a fifth-minute penalty to give the Scarlets an early 10-0 lead.
But any hopes the Scarlets had of a comfortable victory went rather awry midway through the half.
First Treviso outside-half Kris Burton put over a penalty and a drop-goal before the Scarlets lost Stephen Jones to injury in the first quarter.
While the Welshmen were still coming to terms with the loss of their talisman Treviso went into a shock lead when centre Gonzalo Garcia crashed over after good work by the Italian pack.
But from 13-10 down the Scarlets regrouped to score a stunning try.
The region went through the phases before Rhys Priestland, who had taken over the fly-half duties broke through and put Regan King over by the posts with a cheeky pass out of the back door.
By half-time the Scarlets stretched their lead to 10 points with two Priestland penalties, although he did miss another from right in front.
Just as they did in the first half the Scarlets hit Treviso with the early try after the break.
A Treviso kick was half charged down and replacement Dan Newton started a counter attack finished off by flanker Josh Turnbull on 44 minutes.
But a 17-point advantage was whittled away to just three as Treviso hit back with two converted tries in the space of six minutes.
First wing Tommaso Benvenuti finished off a break out of defence by Burton after Scarlets No. 8 had knocked on in the opposition 22.
And scrum-half Fabio Semenzato nipped down the blindside to score Treviso's third try after a five-metre line-out.
The Scarlets were not helped that Priestland was wayward with two penalty kicks.
But Lamont went in for his second try on the hour mark, which not only gave his side a bonus point but also a much-needed eight-point cushion.
Treviso refused to be beaten however and pressed the Scarlets line. From a five metres scrum the Italians looked certain to score through Manoa Vosawai but he was held up brilliantly by Josh Turnbull.
Tries: Lamont 2, King, Turnbull
Con: Jones, Priestland 2
Pen: Jones, Priestland 2
Tries: Garcia, Benvenuti, Semenzato
Con: Burton 3
Scarlets: 15 Rhys Priestland, 14 Morgan Stoddart, 13 Gareth Maule, 12 Regan King, 11 Sean Lamont, 10 Stephen Jones, 9 Tavis Knoyle, 8 Ben Morgan, 7 Josh Turnbull, 6 Rob McCusker, 5 Dominic Day, 4 Vernon Cooper, 3 Simon Gardiner, 2 Matthew Rees (capt), 1 Iestyn Thomas.
Replacements: Ken Owens, Rhodri Jones, Phil John, Jonny Fa'amatuainu, Johnathan Edwards, Martin Roberts, Dan Newton, Scott Williams.
Treviso: 15 Luke McLean, 14 Tommaso Benvenuti, 13 Andrea Pratichetti, 12 Gonzalo Garcia, 11 Andrew Vilk, 10 Kristopher Burton, 9 Fabio Semenzato, 8 Paul Derbyshire, 7 Benjamin Vermaak , 6 Marco Filippucci, 5 ValÃ©rio BernabÃ², 4 Antonio Pavanello, 3 Pedro di Santo, 2 Enrico Ceccato, 1 Matteo Muccignat.
Replacements: 16 Diego Vidal, 17 Ignacio Fernandez Rouyet, 18 Lorenzo Cittadini, 19 Cornelius van Zyl, 20 Manoa Vosawai, 21 Ezio Galon, 22 Edoardo Gori, 23 Joe Maddock.
Referee: Greg Garner