ABSTRACTBackground Diet has been found to be associated with lung function outcomes. However, few studies have investigated longitudinal associations of dietary components (individual foods and/or nutrients) with lung function, and we believe no investigation of the association of dietary pattern as a whole with longitudinal lung function has been conducted. Objective We aimed to investigate if a higher dietary pattern score would attenuate the decline of lung function with age and if this association is modified by smoking status. Design We estimated the association of 2 dietary pattern scores, the Healthy Eating Index 2015 (HEI-2015) and Alternate Mediterranean Diet (AMED), with 3 lung function outcomes, FEV1, FVC, and FEV1/FVC, in two separate cohorts. Stratified analyses were performed in relevant groups, namely among never vs. ever smokers. We performed a meta-analysis to assess the strength of evidence across the cohorts. Results The two cohorts comprise 5,409 participants who met inclusion criteria for analysis. In meta-analysis, a 10-point higher HEI-2015 score was statistically significantly associated with a 16 mL higher FEV1 and a 1-point higher AMED score was statistically significantly associated with a 5 mL higher FEV1 at any point during follow-up. For ever smokers, these associations persisted and increased in magnitude to 24 mL and 6 mL, respectively. Little to no association was found between dietary pattern and the longitudinal rate of decline in lung function. Conclusion We found that dietary pattern has an association with lung function cross-sectionally, but not longitudinally. These associations were modified by smoking status such that a healthier dietary pattern had a stronger positive association in lung function in smokers. While smoking cessation should remain the primary prevention and treatment for lung function decline, our findings provide limited evidence that a healthier dietary pattern associates with better lung health.