Disclosed are 2-heteroaryl substituted benzothiophene and benzofurane compounds of formula (Ia), wherein the substituents are as described within the specification. Further disclosed is a pharmaceutical composition comprising a compound of formula (Ia), the use of a compound of formula (Ia) in a process for the preparation of a labelled compound, and the use of a compound of formula (Ia) in the manufacture of a medicament for use in in vivo metod for measuring amyloid deposits in a subject, wherein the subject is suspected of having a disease or syndrome selected form Alzheimer's disease, familial Alzheimer's disease, Down's Syndrome and homozygotes for the apolipoprotein E4 allele.
