We report on oxetane compounds, as a new class of organic additives for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), promoting both significant conductivity enhancements (in up to three orders of magnitude) and much improved resistance to aqueous medium of PEDOT:PSS spin-cast films. The study unravels the oxetanes´ structural characteristics at the origin of such improvements. It was found that the oxetanes polymerize in the PEDOT:PSS acidic medium to form polyether compounds. Furthermore, hydroxyl-substituted oxetanes can establish covalent cross-linking or hydrogen bond interactions with negatively charged PSS [1,2]. The resultant screening effects between charged PEDOT and PSS reducing coulombic interactions are indicated to cause PEDOT segregation and conformational changes favouring charge transport. We show that ink formulations of PEDOT:PSS incorporating oxetanes, processed by spin-coating or drop-on-demand ink-jet printing, can produce highly conducting thin films either on rigid (glass) or flexible (PET) substrates, and be used as water-resistant electrodes in electronic devices, such as photovoltaic devices and electrochemical field-effect transistors containing aqueous electrolytes. [1] S. M. Jorge, L. F. Santos, A. Galvão, J. Morgado, A. Charas, Adv. Mater. Interfaces, 8, 2100517 (2021). [2] C. Príncipe, S. Silva, M. Matos, L. Santos, J. Morgado, A. Charas, Org. Electron. 125(1), 106985 (2024) Thanks to funding from Fundação para a Ciência e a Tecnologia (FCT) (Portugal) through Instituto de Telecomunicações (contract no. UIDB/50008/2020).