May sick leave/vacation leave/comp time run concurrently with FMLA leave?

Yes as to sick leave and vacation leave; no as to comp time. Generally, an employer may require an employee to use accrued sick or vacation leave while the employee is on FMLA leave for his or her own or a family member’s serious health condition. This is true even where the employee does not want to use accrued leave for this purpose. Where the employer does not require the use of accrued leave, the employee may choose to substitute accrued paid sick or vacation leave for unpaid FMLA leave for a serious health condition. See 29 C.F.R. § 85.207(c).

For the birth or adoption of a child, an employer may require an employee to use accrued vacation or personal leave while the employee is on FMLA leave. It may not require an employee to use sick leave for this purpose. Again, if the employer does not require the use of accrued leave, the employee may choose to substitute accrued paid vacation or personal leave for unpaid FMLA leave for the birth or adoption of a child. See 29 C.F.R. § 85.207(b).

An employee may choose to use any accrued FLSA compensatory time off ("comp time") at the same time as FMLA leave to turn unpaid FMLA leave into paid leave. If an employee does not choose to do so, the employer may require it. An employer may also adopt an across-the-board policy requiring employees on FMLA leave to use any accrued comp time before vacation, sick or personal leave. See 29 C.F.R. § 85.207(f).