The institutionalisation of Smart City Functions (SCF) within local authorities creates significant IT Governance (ITG) challenges, including the need to foster a triadic alignment between the overall organization, the IT function and the SCF. Building on existing literature on ITG, smart cities, and the emerging conversation on Adaptive Governance in the public sector, the following exploratory question has been formulated for this study: How are ITG structural mechanisms implemented in city authorities to oversee and govern smart cities? To address this question, a qualitative multiple case study was carried out across three city authorities in Ireland characterised by diversity in their ITG structural arrangements to govern portfolios of smart city initiatives. From this analysis three types of ITG structural implementation are proposed named: Detached, Integrated, and Traditional. These are compared and discussed in relation to: (1) orientation of each approach; (2) decision-making authority; (3) alignment with the IT function and the overall municipal organization; and (4) the challenge perceived by the SCFs under each ITG arrangement. This research contributes to the academic conversation on adaptive governance, smart cities as well as to the broader ongoing debate on ITG in the public sector.