He failed to feature in Wales' triumphant Six Nations title success but after returning for the Dragons at the back end of the season, Lydiate put himself in the running to be named in Warren Gatland's squad.
His selection was confirmed in late April, the flanker one of 15 Welshman named in the 37-man squad.
And although Lydiate has been a regular starter with Wales under Gatland, he says he was surprised to be named in the touring party.
"I was shocked to be named in the back row," said Lydiate.
"There were so many players who played well in the Six Nations and throughout Europe this year so to actually get one of those places was a massive shock to me.
"It's been a frustrating year, missing six months of the season but Lions selection is the icing on the cake.
"I'm still in shock but I'm really chuffed."
Lydiate is one of four Welsh back rowers in the squad, the most notable of which is tour captain Sam Warburton. Toby Faletau and Justin Tipuric also feature with Tom Croft and Jamie Heaslip offering Gatland further options.
And Lydiate, who is training with the Lions in south Wales this week, is looking to impress.
"There is a good Welsh contingent in the squad but everyone is working hard to improve themselves so hopefully it will be a really good tour," said Lydiate.
"There are so many good back rowers that have been picked so it's up to me personally to train hard and push for my place."