The 18-year-old has enjoyed being part of the tournament's inaugural season and is relishing the prospect of once more leading the line for the young Celts in their return meeting with Ajax in Amsterdam today.
With the strains of the Champions League anthem set to fill the air, Johnstone says that is all music to his ears.
He said: "I've loved the Uefa Youth League. Obviously, I scored against Barcelona and then I had a good performance against Ajax at home, where I thought all the boys were really good.
"I would say it's different to NextGen just because of the whole feel of it. You have the Champions League music on before the games and it does feel like a Champions League match."
The Hoops hit kid said of his last meeting with Ajax: "I was able to show an all-round type of striking role. I held it up well and did well for the team.
"The only thing I missed out on was the goal but, hopefully, I can score again in the competition.
"We needed the three points against Ajax a few weeks ago as it just lifted the spirits among the squad. We just desperately needed a result."