Amid colourful flowers and huge smiles, the official opening of Christchurch's Pacific Heath Clinic was a community celebration.

The new Montreal Street clinic can cater for 5000 patients, double that of the original premises.

Pacific Trust Canterbury CEO Tony Fakahau says the clinic's critical for the region.

"It's an amazing day, a wonderful day and a big milestone for our community. This is a massive achievement and the enrolments are starting to flood in.

"Because it's free for all those under 18 on low incomes, it's a really popular service."