We report on a study of the pentaquark Theta(+)(1540), using a variety of different interpolating fields. We use chirally improved fermions in combination with Jacobi-smeared quark sources to improve the signal and get reliable results even for small quark masses. The results of our quenched calculations, which have been done on a 12(3) x 24 lattice with a lattice spacing of a = 0.148fm, do not provide any evidence for the existence of a Theta(+) with positive parity. We do observe, however, a signal compatible with nucleon-kaon scattering state. For the negative parity the results are inconclusive, due to the potential mixture with nucleon-kaon and N*-kaon scattering states.