We study 3d SCFTs in the superspace formalism and discuss superfields and
on-shell higher spin current multiplets in free 3d SCFTs with N=1,2,3,4 and 6 superconformal symmetry. For N=1 3d SCFTs we
determine the superconformal invariants in superspace needed for constructing
3-point functions of higher spin operators, find the non-linear relations
between the invariants and consequently write down all the independent
invariant structures, both parity even and odd, for various 3-point functions
of higher spin operators.Comment: typos corrected, references added. Accepted for publication in JHE