The group has been blamed for some of the worst atrocities of the Syrian civil war - including the deliberate targeting of civilians.
But according to the nuns, they were treated well by their captors. The rebel video shows the nuns having good rapport with their captors, smiling and exchanging blessings.
An unseen rebel says: "I was so happy to be in communication with you and I hope we can stay in communication, if God decides that. Please say hello to your families for me, and I hope you arrive safely," he adds as the nuns get into the car.
The Greek Orthodox nuns and their three maids were taken after a rebel offensive in the mostly Christian town of Maaloula, where Aramaic is still spoken.
The prisoner exchange is the latest reconciliatory gesture by the Government, which relies on support from minority Alawites and Christians. Negotiations are ongoing to facilitate the release of two archbishops.
- Independent
Missing in Syria
Clerics, journalists and activists are among those missing in Syria and believed to be in the captivity of rebels. Many are thought to have been taken by radical factions, in particular the al-Qaeda breakaway group known as the Islamic State of Iraq and the Levant.
ClericsTwo bishops and a priest have been missing since last April.
ActivistsSyria's leading human rights lawyer, Razan Zaytouni, was abducted with her husband and two other prominent activists from a rebel-held Damascus suburb last December. Nobody claimed responsibility for her abduction, but it came after she wrote an article denouncing the Islamic State.
Abdullah Khalil, also a human rights lawyer, has been missing since last May.
JournalistsThe New York-based Committee to Protect Journalists estimates about 30 international and local reporters are being held.
They include two Spanish journalists, four French journalists, and a Lebanese, a Mauritanian and a Jordanian national of Palestinian origin.
- AP