Mark Robins: 'Could Have Been Different'
In the first half the teams were well matched although Scunthorpe did miss a couple of golden opportunities.
But in the second half Preston came good and took the lead in the 58th minute when Callum Robinson got the ball into the danger zone from out on the left and Johnson swept home his first goal for North End.
The second and decisive goal came on 72 minutes when Chris Humphrey squared the ball for Paul Gallagher to apply the finishing touch.
Robins told reporters: 'I've got no complaints with the result, they did more than us in terms of winning the game. Having said that, we had enough decent opportunities and clear-cut chances so the game could have been different.
'In a 46-game season you know that you're going to come up against an opponent that is probably slightly better than you on the day. They are a good side. I think on paper they've got the strongest squad in the division.'