A gas turbine engine has an annular reverse-flow combustor with a combustor inner liner enclosing a combustion chamber. The inner liner having a dome portion at an upstream end of the combustor and a downstream combustor exit defined between a small exit duct portion and a large exit duct portion. At least one of the dome portion, the small exit duct portion and the large exit duct portion is made of a separately formed hemi-toroidal shell composed of a ceramic matrix composite.