Currently Qatar Airways have a fleet of 9 A300, 1 A310, 2 A319, 12 A320, 2 A321, 15 A330-200, 8 A330-300, 3 A340-600 in total 52... Only the 10 A300/A310 are second hand from many Korean Air/Gurada...
And with a order of 1 A320, 5 A321, 6 A330-200, 5 A330-300, 1 A340-600, 2 A380-800, 6 B777-200LR, 14 B777-300ER in total 40 of them...The A330 still on order will be replacing those A300/A310 which will then be retired soon...
These 10 A300/A310 mainly operate regional routes in Middle-East as these aircraft are not fitted with PTV etc...