Celtic defeated Helsingborg 2-0 in the first leg of their Champions League qualifying playoff match on Tuesday.
Kris Commons and Georgios Samaras scored to give Neil Lennon's side the upper hand heading into next Wednesday's return leg at Parkhead.
With less than two minutes gone Celtic took the lead as Samaras swung a cross from the left wing for Commons to volley past Par Hansson in the Helsingborg goal.
Celtic could not add to their advantage and spent the reminder of the half of the back foot, with Helsingborg new signing Nikola Djurdjic getting in behind Charlie Mulgrew, before unleashing a strike on goal, but Fraser Forster got his body in the way to clear the ball.
However, the Scottish champions claimed a crucial second goal with a quarter of an hour left.
Mulgrew swung a corner in from the right wing, with Samaras rising above the home defence to give Celtic the advantage heading into next Wednesday's second leg at Parkhead.
Meanwhile, Spartak Moscow accounted for Fenerbahce 2-1 in their first leg clash in Russia.
Emmanuel Emenike and Dmitry Kombarov both hit the back of the net in the second half, while Fenerbahce striker Dirk Kuyt scored what could prove to be a crucial away goal at the Luzhniki Stadium.
Emenike latched onto a great cross from Kombarov to break the deadlock on the hour mark but Kuyt had the visitor's level within six minutes.
The former Liverpool attacker capitalised on a goalkeeping error from Andrey Dikan to slot the ball into an empty net.
However, Spartak regained the lead just four minutes later through Kombarov.
Scottish midfielder Aiden McGeady sent in a corner and Kombarov was on hand to smash a low shot past the helpless Mert Gunok.
Elsewhere on Tuesday, Ukrainian giants Dynamo Kiev took control of their tie against Borussia Moenchengladbach after running out 3-1 winners in Germany, Cesar Santin's 38th minute strike earned Copenhagen a 1-0 victory at home to French outfit Lille, while CFR Cluj came from behind in Switzerland to record an impressive 2-1 win at FC Basel courtesy of a second-half goal from Modou Sougou.