The present in situ neutron diffraction study aims to investigate the response of selected lattice planes in the polycrystalline material upon tensile loading. For this purpose, the 0.1C-0.4Mn construction steel was selected as a simple model material. The tensile deformation test was performed in the incremental mode in which each individual deformation step was followed by unloading. The neutron diffraction spectra were collected both upon loading and unloading and the behavior of the diffraction profiles in the elastic as well as in the plastic region of the deformation curve was examined in detail. Whereas the behavior of the lattice strains during straining and the evolution of the residual intergranular strains have already been described in other papers, the present work is focused mainly on profile broadening effects measured in the same deformation regime. The estimate of microstrain evolution was done by using the single-line profile analysis method. Comparison of microstrain values in the loaded/unloaded state and in the elastic and plastic regions offers an interesting possibility to estimate the contribution of the type II and type III microstrains.