Nanoconfinement can profoundly change the bulk characteristics. The question of conformational changes under one-dimensional confinement is recurrent in polymer physics. Very few works addresses this question because of the hard experimental challenge and the complex analysis of the signal. Here, the conformation of polystyrene chains shaped by wetting, in nanotubes or nanorods is for the first time determined at 3 dimensions. Polystyrene chains (molecular weight samples from 38 kDa to 310 kDa) confined in AAO nanopores as large as the size of the pore diameters (from 35 to 180 nm) are probed, revealing the invariance with respect to the bulk-like conformation for polystyrene chains up to 301 kDa confined down to 35 nm diameter nanopores.