The WAXS diffractograms of random ethylene copolymers were analyzed for samples rapidly quenched, annealed, or isothermally crystallized. Comonomers studied include 1-decene, 1-hexene, 4-methylpentene, norbornene, and dicyclopentadiene in a range of concentration that includes semicrystalline and amorphous copolymers at ambient temperature. Only crystalline reflections corresponding to the orthorhombic structure were identified in these copolymers. Focus is given to analyze the contribution of the concentration of comonomer as well as the comonomer type in the angular position of the amorphous halo. For samples quenched to 23 degreesC the peak value scales linearly and in inverse proportion with the concentration of comonomer in the copolymer reflecting the increase of the average backbone carboncarbon intermolecular distance associated with the interlamellar region. With increasing temperature, a progressive melting of crystallites changes the comonomer composition of the amorphous region and leads to a temperature coefficient of the peak position of the halo that is a function of the concentration of comonomer in the chain.