Deciding what do to with an old 401(k) or other workplace retirement plan may not seem complicated, but a surprising number of participants do not understand which options are available to them, according to a survey by Fidelity Investments.

The Boston-based fund giant found that 30% of Fidelity retirement plan participants who made a job transition are unsure of what to do with their old workplace retirement savings. The results are particularly noteworthy since Fidelity is the top provider of workplace retirement savings plans as well as individual retirement accounts.

“For years, we’ve had the grid on comparing various options,” says Sarah Walsh, vice president with Fidelity Investments. “But clearly, people are looking for more guidance.”

One step the company has taken as a result of the study’s findings has been to add to its Fidelity Viewpoints investor publication an article that provides a side-by-side comparison of options available to investors.

“We can certainly be a little more explicit with some of the content around the options,” says Walsh.

The study surveyed more than 1,000 participants who had left their employers at least four months prior. Fidelity data shows that about one third of participants move their money from a former employer’s plan within four months after a job transition. But those who remain in their old plan do so for a variety of reasons.

Of the survey respondents, 27% indicated that a lack of time or mind share has prevented them from taking any action. And 71% said they are consciously keeping their assets in an old plan for the time being: The top reason, given in 59% of those cases, was satisfaction with the plan features or services and access to specific investments.

Larger plan sponsors often offer more attractive options than can typically be found in IRAs. “If they’ve made a conscious decision to stay in their plan for specific reasons, I think that’s a perfectly good reason stay in,” says Walsh. “The risk comes is people are doing it because they don’t understand their options or don’t have time to think about it.”

When respondents were asked if they are planning to take any action within the next year, 24% indicated they were not sure, and 18% said they were going to move the money to an IRA or their current employer’s workplace savings plan. But the majority—57%--indicated that they were planning to keep their investments in their old plan for the next 12 months.