We describe several methods for optoelectronic processing of 3D images based in digital holography. In all cases, phase-shift digital holography is used to record the complex amplitude distribution associated to the diffraction field generated by 3D objects illuminated with coherent light. First, we review a technique to encrypt a 3D image by using digital holography. Encryption is performed by using random phase codes as key functions. In this way, it is possible to send secure 3D information through conventional digital communication lines. In our approach, decryption is carried out digitally. Next we describe both, digital and optical reconstruction of 3D images starting from digital holograms. Finally, we show how to perform 3D pattern recognition with high discrimination based in the above techniques. Experimental results are presented.