An organisation's portfolio of new product development (NPD) projects represents its potential for survival. Innovation ambidexterity holds the key to longevity. Accordingly, selecting the right projects for a portfolio critically impacts organisational success, both in the short and longer term. Selecting for successful portfolios is further complicated in dynamic, highly competitive and highly regulated markets. Furthermore, in current economies that demand value from investment, decision-making around project selection for the portfolio becomes even more crucial. However, there is a dearth of discussion and empirical evidence that focuses on project portfolio selection and more specifically in contexts of ambidexterity and ongoing change. Moreover, the tensions between exploratory and exploitative projects are likely to be made salient during project portfolio selection, and manifest in conflicts between different selection options, yet these tensions have not yet been addressed in the portfolio selection literature. Drawing on the current and heretofore non-connected literatures across fields of ambidexterity and paradox, project portfolio selection, cognition and performance control, this paper proposes an initial conceptual model of the factors that impact project portfolio selection and ambidexterity. This paper contributes to a greater appreciation of the pivotal role of project portfolio selection, as distinct from project and portfolio management, in generating a portfolio that drives organisational success. Moreover, it identifies performance measures and managing conflict as important determinants of project portfolio ambidexterity. Future work is required to enhance and validate this model. (C) 2017 The Authors. Published by Elsevier B.V.