ERBB2 and neoplasm: This study demonstrated that the HER2-targeted sdAb [68Ga]Ga-DOTA-GA-RAD202.1 without HIS-tag is superior for PET imaging of HER2-positive tumors compared with the sdAb [68Ga]Ga-DOTA-GA-RAD202 with HIS-tag due to the higher tumor-to-organ ratios with the former.