The UN Security Council is due to meet in New York to discuss the issue of child solders in Chad.
Rehabilitation is likely to take several months
Thousands of boys are thought to be fighting in the national army, as well as rebel and paramilitary groups.
The meeting comes just days after Human Rights Watch criticised Chad's government for breaking promises to release child soldiers from the army.
Under a deal, just 400 child soldiers have been released and they arrived in a rehabilitation centre in 10 days ago.
The BBC's Stephanie Hancock says many of the children in the centre of the capital, N'Djamena, appear to be between 13 and 16 years old, but some are clearly much younger.
Sixteen-year-old "Saeed"', who says he was with the rebels for two years, says they have been welcomed very warmly.
"Before, I didn't know life could be like this. Here we have everything - there is water and food, and to see trees around us is wonderful."
"Juma" says he is 13 years old, but aid workers suspect he is no more than eight or nine.
"There, we didn't play games, all we did was fight. I haven't made war in the whole time I have been here at the centre.
"We were always worried about security, but now we play games like football and I have clothes to play sports in."
Since they arrived at the rehabilitation centre set up by the government and the UN children's fund, Unicef, the former boy soldiers follow a strict routine of prayer, rest and play.
The children pass their days playing cards and volleyball, and have lessons in basic literacy, our reporter says.
Supervisors say they hope that in a few months time the boys can return to their families but the road back to normality will be a long one.
"Some of the children were very violent when they arrived, but gradually they are changing their behaviour," says Brahim Abdulai, the centre's supervisor.
"Some are also very conscious that they are living in a different state from before, and that they must try to forget the violence and what happened to them," he said.
"We are teaching them to love their friends, and not to get angry if someone does something bad to them."
Observers estimate that there are between 7,000 and 10,000 child soldiers on Chadian territory, either in the national army, or in rebel and paramilitary groups.