The \(p^\infty \) -fine Selmer group of an elliptic curve E over a number field F is a subgroup of the classical \(p^\infty \) -Selmer group of E over F. Fine Selmer group is closely related to the 1st and 2nd Iwasawa cohomology groups. Coates-Sujatha observed that the structure of the fine Selmer group of E over a p-adic Lie extension of a number field is intricately related to some deep questions in classical Iwasawa theory; for example, Iwasawa’s classical \(\mu \) -invariant vanishing conjecture. In this article, we study the properties of the \(p^\infty \) -fine Selmer group of an elliptic curve over certain p-adic Lie extensions of a number field. We also define and discuss \(p^\infty \) -fine Selmer group of an elliptic curve over function fields of characteristic p and also of characteristic \(\ell \ne p.\) We relate our study with a conjecture of Jannsen.