We investigate the effects of a width increase on the electronic properties of ballistic quantum wires by evaluating the local density of states and the conductance. A local widening of the quantum wire introduces dip structures in addition to the well-known steplike structures of the conductance. The mode coupling between the bound state and the extended state is the origin of these structures. The quasibound and the complete backscattering state are clearly shown to arise as a result of mode couplings. We also point out that a smooth variation of the width of the quantum wires does not remove these quasibound states.