Molecular imaging using PET plays an important role for the diagnosis of different diseases. Immuno-PET combines the utilization of PET radionuclides and antibodies/proteins/peptides, presenting a popular method for imaging of different diseases, including cancer. Zr-89 is an attractive radiometal for immuno-PET but far from ideal due to its high radiation dose for the patients. However, its long half-life is sometimes advantageous and suitable for labelling antibodies, proteins and other biomolecules. This review compiles opportunities and applications for using Zr-89 in preclinical and clinical practice. It contains either results from for its production, preclinical and clinical studies.