Apathy is common in aging and generally defined on the basis of three dimensions: lack of initiative, lack of interest and emotional blunting. Curiously, no study until now has examined the associations and dissociations between these dimensions in elderly people (with or without dementia). These questions were addressed in two studies. In the first study, we explored the distribution of scores and the relationships between the three dimensions of apathy in 56 patients with dementia, focusing mainly on lack of initiative and lack of interest. Apathy was hetero-evaluated with the Apathy Inventory (AI), a scale widely used to assess the apathy dimensions in aging. In the second study, given the AI's limitations, we investigated in more detail the relationship between lack of initiative and interest in 115 elderly people using a new questionnaire specifically designed to assess these two dimensions. Results showed that lack of initiative was closely related to lack of interest (Study 1). Although we used a more specific questionnaire, these facets of apathy did not constitute two separable dimensions, but reflected a common main factor of apathy in aging (Study 2). Thus, the distinction between lack of initiative and lack of interest seems questionable. Only a multifactorial approach that includes the various psychological factors involved in apathy would enable one to gain a better understanding of the different manifestations of apathy and to highlight possible dissociations between them.