World Cup Qualifying Results : Portugal a 1-0 Sweden
CR7 headed past Sweden goalkeeper Andreas Isaksson in the 82nd minute from six yards out after a fine left wing cross from Miguel Veloso.
Ronaldo, who now has 29 goals total this season for club and country.
The Portuguese have a one-goal advantage ahead of the second leg in Solna next Tuesday where hope for Sweden depends upon superstar striker Zlatan Ibrahimovic. With Ibra's help, Sweden hopes to go the finals in Brazil.
Sweden went into the match unbeaten in Portugal, having won four and drawn three of the previous seven meetings between the sides.
Portugal were boosted by Ronaldo's return from suspension although they were without attacking midfielder Danny and goalkeeper Anthony Lopes, who are both injured.
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