WO -dimensional electron plasma in nanometer size field effect transistors can oscillate in Terahertz (THz) frequencies, far beyond transistors fundamental cut-of frequencies. Interest in using nanometer field effect transistors (FETs) for THz applications was initiated in the early ‗90s by the theoretical work of Dyakonov and Shur who predicted that the channel of a FET could act as a resonator for plasma waves and that THz radiation can be efficiently rectified FET. Rectification and detection of THz radiation is also possible in the non-resonant case, (low electron mobility) when plasma waves decay at the distance smaller than the channel length. Typical length of this region ranges from 30nm to 300nm [3]. Therefore, both resonant and nonresonant plasma wave THz detection requires nanometer scale FETs. For recent reviews see [1] and [2]. The real large scale interest in using FETs as THz detectors started around 2004 after first experimental demonstration of sub-THz and THz detection in silicon CMOS FETs [3,4]. Both pioneering works have clearly stated importance of Si- CMOS FETs which present the advantages of room temperature operation, very fast response times, easy on-chip integration with read-out electronics and high reproducibility leading to straight-forward array fabrication. We propose a review of the most important and recent results on terahertz detection using nanometer size FETs. The subjects were selected in a way to stress physical limits of FET detectors and possible new developments [5-9]. We would like to address the basic physics related problems like power dependence of the photoresponse [2], temperature dependence, of the response [5], and helicity sensitive detection [6]. Until now, most of the work on nanometer FETs detectors considered mainly THz imaging applications. We show also the progress in the application of nanometer FETs as detectors in THz wireless communication [7]. Finally we would like to present results from THz detection by grapheme transistors [8] and discuss possible developments of future THz detectors using nanowires.