A new variety of LiMnO2 exhibiting a layered structure has been obtained by chimie douce reaction from alpha-NaMnO2. This material crystallises in the monoclinic system. Rietveld refinement of the X-ray diffraction pattern shows clearly that the MnO6 octahedra are strongly distorted as the result of the Jahn-Teller effect on the trivalent manganese ions. Moreover, a small amount of manganese is present within the lithium layer, contrary to the alpha-NaMnO6 precursor phase which exhibits a strictly bidimensional structure.