It is important to identify selective ligands for the estrogen receptor subtypes ER$alpha$ or ER$eta$ to evaluate them as pharmaceutical targets in breast cancer. To develop ER$eta$-selective ligands as PET imaging agents, a series of aryl indazole estrogen analogues substituted at the C3 position with fluoroethyl and fluoropropyl groups were synthesized and evaluated for their relative binding affinities and selectivities for ER$alpha$ vs ER$eta$. The fluoroethylated indazole estrogen (FEIE, 1i) and fluoropropylated indazole estrogen (FPIE, 1h) showed 41- fold and 17-fold ER$eta$/ER$alpha$ selectivity, respectively. However, their binding affinities to ER$alpha$ and ER$eta$ were very low.