We discuss model-independent methods to measure the P-parity of the Θ+-pentaquark, in the simplest processes of photo-production, , using definite relations between those polarization observables which depend on the P-parity of the Θ+-baryon (with respect to the NK system). One method, which holds for any photon energy and any K-meson production angle, is based on the relation between the ΣB asymmetry (induced by a linearly polarized photon beam with unpolarized target) and the Dnn component of the depolarization tensor (for an unpolarized photon beam). Another method, which applies in collinear kinematics (or in threshold conditions), is related to the sign of the Dnn component with a linearly polarized photon beam.