Breast carcinomas are prevalent in females around the world. However, current diagnostic and therapeutic measures are limited by low sensitivity and specificity. Breast carcinomas are found to over-express neuropeptide Y (NPY) Y1 receptors, whose functional roles in tumour growth and metastasis have been demonstrated.1 Therefore, Y1 receptor is a valuable target for diagnosis and treatment of breast carcinomas. Here we describe the synthesis of 38 truncated NPY analogues as models for Y1-specific peptidic radioimaging agents used in positron emission tomography. These sequences are based on the previously reported Y1 antagonist BVD15 scaffold.2 Different strategies to improve Y1 affinity and metabolic stability were investigated. We found that a basic amino acid residue at position 4 improved Y1 affinity, and Arg4 substituted analogues possessed excellent tolerability to N-terminal aryl capping groups. While various conjugations at Lys4 ε-amine were tolerated, a further N-terminal aryl group sacrificed affinity. Replacing Asn2 by a Lys retained affinity, and a NOTA conjugation at its ε-amine was well tolerated. Modifications to position 5 were limited to small prosthetic groups. Finally, incorporation of D-amino acids for stability enhancement caused loss of Y1 affinity.