There is a relationship between choosing an activity and its duration, especially for non-mandatory activities. A number of studies have analyzed the decisions about an activity type and its duration independently, while some others have used joint models. This paper contributes to the body of knowledge using Nested-logit and copula-based models for assessing the existence of interdependency between, or a hierarchy of, the choice of non-mandatory activity and its relative duration. In the case of the nestedlogit model, it is assumed that error terms of these decisions are interrelated, although one is in uenced by another. In contrast, the copula-based model can facilitate making a spatial error correlation between observational units without imposing the assumption of restrictive distribution on the dependency structures between the error components. The data available from Qazvin, a city in Iran, were used for estimating both Nested-logit and copula-based models and the best variables explaining both choices for each model were selected. The Final models were compared in terms of log-likelihood at convergence and adjusted likelihood ratio index. The results indicated that there were some common in uential observed and unobserved factors between these decisions. Also, the copula-based joint model with  2 0 equal to 0. 134 outperformed Nested-logit models and provided better explanatory power.