Lamont started and finished the try scoring for a crucial win
The Scarlets survived a dogged Treviso fightback to claim a vital bonus-point win in Heineken Cup pool five.
Tries from Sean Lamont and Regan King put them in front, but Stephen Jones was injured as a Gonzalo Garcia try and Chris Burton's boot kept things close.
John Turnbull's try made it 30-13, but quick scores from Tommaso Benvenuti and Fabio Semenzato cut the gap to three.
Lamont's second try secured the bonus, huge defence needed to deny Treviso's forwards and send them home pointless.
The win puts the Welsh side level with Perpignan on 10 points, one behind group leaders Leicester.
The Scarlets' build-up had been dominated by their problems at tight-head, Wales Under-20 prop Simon Gardiner registered and named in the starting XV with Deacon Manu, Rhys Thomas and Peter Edwards on the injury list.
But front-row worries were soon forgotten as Lamont crossed for a second-minute try, the winger profiting from fine build-up play, quick recycling and Stephen Jones' vision to spot the Scot on the angle.
Jones converted and added a penalty, but Burton clawed the dogged Italians into contention with a penalty and drop-goal.
Stephen Jones' knee injury will trouble both the Scarlets and Wales
The home side then suffered a double blow as Jones went off with a worrying knee injury, before good work by the Treviso pack saw Garcia cross for a try that was improved by Burton to give his team a 13-10 lead.
The Scarlets' running game was on fire, though, and after deft interplay between forwards and backs Rhys Priestland made a delightful break before sending King under the posts for a superb score.
Priestland - who had been moved from full-back to replace Jones at 10 - converted and added a penalty after a bullocking Ben Morgan run.
Burton was wayward with another shot at goal, before Priestland blotted his copybook with an awful miss from in front of goal.
The in-form Scarlet - whose displays have him pushing for Wales recognition - made amends with his second successful penalty to make it 23-13 at the break.
The game looked safe after just four minutes of the second period, replacement Dan Newton breaking from deep, with the attack carried forward by Gareth Maule before Turnbull crossed for a superb converted try.
Another rampant Morgan run nearly brought the bonus-point try, but the burly number eight lost the ball near the Treviso line.
In a dramatic turnaround Burton sparked a scintillating length-of-the-field counter-attack that ended with Benvenuti crossing for a stunning try that was converted by Burton.
The powerful Treviso forwards then took a grip, winning a short-range penalty after a series of driving mauls.
Rhys Priestland impressed at 10 but struggled with his goal kicking
The Italians kicked to touch, and from the line-out scrum-half Semenzato darted into a blind-side gap for his team's third try, Burton's fine conversion from the touchline cutting the Scarlets' lead to just three points.
Priestland missed a simple 60th-minute penalty and was held up over the line after a long Scarlets attack.
Tavis Knoyle quickly fired the ball out, though, finding Lamont who crossed for the bonus-point try, only to see Priestland miss the conversion.
Treviso mounted a series of huge forward attacks on the home side's line that seemed certain to yield a try, but heroic defence - notably from Turnbull - somehow kept them at bay.
The Scarlets will be desperate for another win in next week's reverse fixture in Italy, but - having lost to Treviso at the Stadio Monigo in the Magners League this season - they will need to be at the top of their game.
Scarlets: Priestland, Stoddart, Maule, King, Lamont, S. Jones, Knoyle, I. Thomas, M. Rees, Gardner, Cooper, Day, McCusker, Turnbull, Morgan. Replacements: Newton for S. Jones (18), Roberts for Knoyle (66), R. Jones for I. Thomas (78), Owens for M. Rees (62), John for Gardner (51), Fa'amatuainu for Day (66), J. Edwards for McCusker (59). Not Used: S. Williams.
Benetton Treviso: McLean, Benvenuti, Pratichetti, Garcia, Vilk, Burton, Semenzato, Muccignat, Ceccato, Di Santo, A. Pavanello, Bernabo, Filippucci, Vermaak, Derbyshire. Replacements: Maddock for Pratichetti (48), Rouyet for Muccignat (48), Vidal for Ceccato (48), Cittadini for Di Santo (48), van Zyl for A. Pavanello (24), Vosawai for Derbyshire (57). Not Used: Galon, Gori.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.