Surface and leaky modes in grounded slabs with omega particles are studied. Two distinct omega-like media are considered: an omega medium and a pseudochiral omega medium. Depending on the orientation of the omega inclusions inside the slab, hybrid and transversal solutions are obtained. The influence of the intensity of the magnetoelectric coupling is investigated, leading to a new physical result: proper leaky modes do occur in a lossless grounded pseudochiral omega slab. The lack of symmetry in this medium is the most important feature that distinguishes it from the omega case. Potential new applications using the pseudochiral omega medium are addressed.